diff --git a/src/main/java/com/assu/server/domain/deviceToken/entity/DeviceToken.java b/src/main/java/com/assu/server/domain/deviceToken/entity/DeviceToken.java
index 4d98454e..f0ce00f5 100644
--- a/src/main/java/com/assu/server/domain/deviceToken/entity/DeviceToken.java
+++ b/src/main/java/com/assu/server/domain/deviceToken/entity/DeviceToken.java
@@ -18,7 +18,7 @@ public class DeviceToken extends BaseEntity {
     @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name="member_id", nullable=false)
     private Member member;
 
-    @Column(nullable=false, length=200, unique=true)
+    @Column(nullable=false, length=200)
     private String token;
 
     @Setter
diff --git a/src/main/java/com/assu/server/domain/deviceToken/repository/DeviceTokenRepository.java b/src/main/java/com/assu/server/domain/deviceToken/repository/DeviceTokenRepository.java
index ee0c8349..95c1fcfb 100644
--- a/src/main/java/com/assu/server/domain/deviceToken/repository/DeviceTokenRepository.java
+++ b/src/main/java/com/assu/server/domain/deviceToken/repository/DeviceTokenRepository.java
@@ -20,4 +20,10 @@ public interface DeviceTokenRepository extends JpaRepository<DeviceToken, Long>
     void deactivateTokens(@Param("tokens") List<String> tokens);
 
     Optional<DeviceToken> findByToken(String token);
+
+    // 같은 회원 + 같은 토큰 있는지 확인
+    Optional<DeviceToken> findByMemberIdAndToken(Long memberId, String token);
+
+    // 같은 회원이 가진 모든 토큰 (비활성화용)
+    List<DeviceToken> findAllByMemberId(Long memberId);
 }
diff --git a/src/main/java/com/assu/server/domain/deviceToken/service/DeviceTokenServiceImpl.java b/src/main/java/com/assu/server/domain/deviceToken/service/DeviceTokenServiceImpl.java
index 9d4cabb1..fe37ddd4 100644
--- a/src/main/java/com/assu/server/domain/deviceToken/service/DeviceTokenServiceImpl.java
+++ b/src/main/java/com/assu/server/domain/deviceToken/service/DeviceTokenServiceImpl.java
@@ -21,19 +21,41 @@ public class DeviceTokenServiceImpl implements DeviceTokenService {
     @Transactional
     @Override
     public Long register(String tokenId, Long memberId) {
-        Member member = memberRepository.findMemberById(memberId).orElseThrow(
-            () -> new GeneralException(ErrorStatus.NO_SUCH_MEMBER)
-        );
-        if (member == null) {
-            throw new DatabaseException(ErrorStatus.NO_SUCH_MEMBER);
+        Member member = memberRepository.findMemberById(memberId)
+                .orElseThrow(() -> new GeneralException(ErrorStatus.NO_SUCH_MEMBER));
+
+        // 1) 같은 회원 + 같은 토큰이 이미 있으면 → active = true 로만 복구
+        //    (가장 정확한 쿼리: findByMemberIdAndToken)
+        var sameTokenOpt = deviceTokenRepository.findByMemberIdAndToken(memberId, tokenId);
+        if (sameTokenOpt.isPresent()) {
+            DeviceToken exist = sameTokenOpt.get();
+            exist.setActive(true);
+            deviceTokenRepository.save(exist);
+            return exist.getId();
+        }
+
+        // 2) 같은 회원 + 다른 토큰 → 그 회원의 기존 active 토큰 전부 비활성화
+        //    (현재 보유 메서드 활용: 활성 토큰 문자열 가져와 deactivate)
+        var activeTokens = deviceTokenRepository.findActiveTokensByMemberId(memberId);
+        if (!activeTokens.isEmpty()) {
+            // 현재 등록하려는 tokenId 와 다른 것들만 비활성화
+            var toDeactivate = activeTokens.stream()
+                    .filter(t -> !t.equals(tokenId))
+                    .toList();
+            if (!toDeactivate.isEmpty()) {
+                deviceTokenRepository.deactivateTokens(toDeactivate);
+            }
         }
 
-        DeviceToken dt = deviceTokenRepository.findByToken(tokenId)
-                .map(deviceToken -> { deviceToken.setActive(true); return deviceToken; })
-                .orElse(DeviceToken.builder().member(member).token(tokenId).active(true).build());
-        deviceTokenRepository.save(dt);
+        // 3) 새 토큰 insert (다른 회원이 같은 토큰을 갖고 있어도 상관 없이 insert)
+        DeviceToken newToken = DeviceToken.builder()
+                .member(member)
+                .token(tokenId)
+                .active(true)
+                .build();
+        deviceTokenRepository.save(newToken);
 
-        return dt.getId();
+        return newToken.getId();
     }
 
     @Transactional