diff --git a/classes/command_groupsadd.php b/classes/command_groupsadd.php
new file mode 100644
index 0000000..01a9efa
--- /dev/null
+++ b/classes/command_groupsadd.php
@@ -0,0 +1,131 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Workflow script command to add role members to groups.
+ *
+ * @package   block_workflow
+ * @copyright 2021 Takayuki Nagai, Center for Information Science, Kyoto Institute of Technology
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die('Direct access to this script is forbidden.');
+
+/**
+ * The command to add role members to a list of groups identified by idnumbers
+ *
+ * @package    block
+ * @subpackage workflow
+ * @copyright  2021 Takayuki Nagai
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ *
+ */
+class block_workflow_command_groupsadd extends block_workflow_command {
+    /**
+     * Validate the syntax of this line, and ensure that it is correct for
+     * this context
+     * @param String    args    The list of arguments to the command
+     * @param stdClass  state   The state object for this step_state
+     * @throws block_workflow_invalid_command_exception
+     * @return stdClass data    An object containing the validated data
+     *                          which will be used for execution
+     *
+     * Exceptions are thrown if:
+     * * an invalid role is specified for the newrole; or
+     * * an invalid role is specified for any of the role assignments.
+     *
+     * Note: No exception is thrown if there are no users with specified role.
+     */
+    public function parse($args, $step, $state = null) {
+        // We'll return the components in an object.
+        $data = new stdClass();
+        $data->errors = array();
+
+        if ($state) {
+            $data->context = $state->context();
+        }
+
+        // Break down the line. It should be in the format
+        // role from idnumber1 idnumber2 ... idnumberN
+        // with any number of group idnumbers.
+        $line = preg_split('/[\s+]/', $args);
+
+        // Grab the role name.
+        $data->role = parent::require_role_exists(array_shift($line), $data->errors);
+
+        // Shift off the 'to' component.
+        $to = array_shift($line);
+        if ($to !== 'to') {
+            $data->errors[] = get_string('invalidsyntaxmissingto', 'block_workflow');
+            return $data;
+        }
+
+        // Check whether the specified groups exist and fill the list of target users.
+        $data->groups = array();
+        $data->users = array();
+
+        if($state) {
+            // Get users who has the specified role.
+            $thisrole = $data->role;
+            if ($thisrole) {
+                // We can only get the list of users if we've got a specific context.
+                $data->users = array_merge($data->users, parent::role_users($thisrole, $data->context));
+            }
+
+            $courseid = context::instance_by_id($state->contextid)->get_course_context()->instanceid;
+
+            // Check that each group with the specified idnumber exists
+            foreach ($line as $idnumber) {
+                // Check that the group exists.
+
+                // (courseid,idnumber) -> (group)
+                if($thisgroup = groups_get_group_by_idnumber($courseid,$idnumber)) {
+                    $data->groups[] = $thisgroup;
+                } else {
+                    $data->errors[] = get_string('invalididnumber', 'block_workflow');
+                }
+            }
+
+            // Check that some groups were specified.
+            if (count($data->groups) <= 0) {
+                $data->errors[] = get_string('nogroupsspecified', 'block_workflow');
+                return $data;
+            }
+        }
+
+        return $data;
+    }
+
+    /**
+     * Execute the command given the line of arguments and state of the
+     * step.
+     *
+     * Validation is automatically performed before continuing.
+     * @param String    args    The list of arguments to the command
+     * @param stdClass  state   The state object for this step_state
+     */
+    public function execute($args, $state) {
+        global $CFG;
+        require_once("$CFG->dirroot/group/lib.php");
+
+        $data = $this->parse($args, $state->step(), $state);
+        foreach ($data->groups as $group) {
+            foreach ($data->users as $user){
+                groups_add_member($group->id,$user->id,'block_workflow', $state->id);
+            }
+        }
+    }
+}
diff --git a/classes/command_groupsremove.php b/classes/command_groupsremove.php
new file mode 100644
index 0000000..4091c3e
--- /dev/null
+++ b/classes/command_groupsremove.php
@@ -0,0 +1,131 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Workflow script command to remove role members from groups.
+ *
+ * @package   block_workflow
+ * @copyright 2021 Takayuki Nagai, Center for Information Science, Kyoto Institute of Technology
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die('Direct access to this script is forbidden.');
+
+/**
+ * The command to remove role members from a list of groups identified by idnumbers
+ *
+ * @package    block
+ * @subpackage workflow
+ * @copyright  2021 Takayuki Nagai
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ *
+ */
+class block_workflow_command_groupsremove extends block_workflow_command {
+    /**
+     * Validate the syntax of this line, and ensure that it is correct for
+     * this context
+     * @param String    args    The list of arguments to the command
+     * @param stdClass  state   The state object for this step_state
+     * @throws block_workflow_invalid_command_exception
+     * @return stdClass data    An object containing the validated data
+     *                          which will be used for execution
+     *
+     * Exceptions are thrown if:
+     * * an invalid role is specified for the role; or
+     * * an invalid group is specified for any of the group assignments.
+     *
+     * Note: No exception is thrown if there are no users with specified role.
+     */
+    public function parse($args, $step, $state = null) {
+        // We'll return the components in an object.
+        $data = new stdClass();
+        $data->errors = array();
+
+        if ($state) {
+            $data->context = $state->context();
+        }
+
+        // Break down the line. It should be in the format
+        // role from idnumber1 idnumber2 ... idnumberN
+        // with any number of group idnumbers.
+        $line = preg_split('/[\s+]/', $args);
+
+        // Grab the role name.
+        $data->role = parent::require_role_exists(array_shift($line), $data->errors);
+
+        // Shift off the 'from' component.
+        $from = array_shift($line);
+        if ($from !== 'from') {
+            $data->errors[] = get_string('invalidsyntaxmissingfrom', 'block_workflow');
+            return $data;
+        }
+
+        // Check whether the specified groups exist and fill the list of target users.
+        $data->groups = array();
+        $data->users = array();
+
+        if($state) {
+            // Get users who has the specified role.
+            $thisrole = $data->role;
+            if ($thisrole) {
+                // We can only get the list of users if we've got a specific context.
+                $data->users = array_merge($data->users, parent::role_users($thisrole, $data->context));
+            }
+
+            $courseid = context::instance_by_id($state->contextid)->get_course_context()->instanceid;
+
+            // Check that each group with the specified idnumber exists
+            foreach ($line as $idnumber) {
+                // Check that the group exists.
+
+                // (courseid,idnumber) -> (group)
+                if($thisgroup = groups_get_group_by_idnumber($courseid,$idnumber)) {
+                    $data->groups[] = $thisgroup;
+                } else {
+                    $data->errors[] = get_string('invalididnumber', 'block_workflow');
+                }
+            }
+
+            // Check that some groups were specified.
+            if (count($data->groups) <= 0) {
+                $data->errors[] = get_string('nogroupsspecified', 'block_workflow');
+                return $data;
+            }
+        }
+
+        return $data;
+    }
+
+    /**
+     * Execute the command given the line of arguments and state of the
+     * step.
+     *
+     * Validation is automatically performed before continuing.
+     * @param String    args    The list of arguments to the command
+     * @param stdClass  state   The state object for this step_state
+     */
+    public function execute($args, $state) {
+        global $CFG;
+        require_once("$CFG->dirroot/group/lib.php");
+
+        $data = $this->parse($args, $state->step(), $state);
+        foreach ($data->groups as $group) {
+            foreach ($data->users as $user){
+                groups_remove_member($group->id,$user->id,'block_workflow', $state->id);
+            }
+        }
+    }
+}
diff --git a/locallib.php b/locallib.php
index c384e72..cf00b77 100644
--- a/locallib.php
+++ b/locallib.php
@@ -34,6 +34,8 @@
 require_once($CFG->dirroot . '/blocks/workflow/classes/command.php');
 require_once($CFG->dirroot . '/blocks/workflow/classes/command_assignrole.php');
 require_once($CFG->dirroot . '/blocks/workflow/classes/command_email.php');
+require_once($CFG->dirroot . '/blocks/workflow/classes/command_groupsadd.php');
+require_once($CFG->dirroot . '/blocks/workflow/classes/command_groupsremove.php');
 require_once($CFG->dirroot . '/blocks/workflow/classes/command_override.php');
 require_once($CFG->dirroot . '/blocks/workflow/classes/command_setactivitysetting.php');
 require_once($CFG->dirroot . '/blocks/workflow/classes/command_setactivityvisibility.php');