diff --git a/src/main/java/treehouse/server/api/user/persistence/FcmTokenRepository.java b/src/main/java/treehouse/server/api/user/persistence/FcmTokenRepository.java
index 7cd2c87..8dc210e 100644
--- a/src/main/java/treehouse/server/api/user/persistence/FcmTokenRepository.java
+++ b/src/main/java/treehouse/server/api/user/persistence/FcmTokenRepository.java
@@ -14,7 +14,11 @@ public interface FcmTokenRepository extends JpaRepository<FcmToken, Long> {
 
     void deleteAllByUser(User user);
 
+    void deleteByUser(User user);
+
+    boolean existsByUser(User user);
+
     boolean existsByUserAndToken(User user, String token);
 
-    List<FcmToken> findAllByUser(User user);
+//    List<FcmToken> findAllByUser(User user);
 }
diff --git a/src/main/java/treehouse/server/global/entity/User/FcmToken.java b/src/main/java/treehouse/server/global/entity/User/FcmToken.java
index 3fecbf1..4f339e2 100644
--- a/src/main/java/treehouse/server/global/entity/User/FcmToken.java
+++ b/src/main/java/treehouse/server/global/entity/User/FcmToken.java
@@ -19,7 +19,7 @@ public class FcmToken extends BaseDateTimeEntity {
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long id;
 
-    @ManyToOne(fetch = FetchType.LAZY)
+    @OneToOne
     private User user;
 
     private String token;
diff --git a/src/main/java/treehouse/server/global/exception/GlobalErrorCode.java b/src/main/java/treehouse/server/global/exception/GlobalErrorCode.java
index 57f457b..e81761e 100644
--- a/src/main/java/treehouse/server/global/exception/GlobalErrorCode.java
+++ b/src/main/java/treehouse/server/global/exception/GlobalErrorCode.java
@@ -106,6 +106,7 @@ public enum GlobalErrorCode implements BaseErrorCode{
     PHONE_AUTH_TIMEOUT(BAD_REQUEST, "NCP400_3", "인증 시간이 초과되었습니다."),
 
     FCM_ALREADY_EXISTS_TOKEN(BAD_REQUEST, "FCM400_1", "이미 저장되어 있는 FCM 토큰입니다."),
+    FCM_TOKEN_NOT_EXISTS(BAD_REQUEST,"FCM400_2", "해당 유저의 FCM Token 이 존재하지 않습니다."),
     FCM_ACCESS_TOKEN_REQUEST_ERROR(INTERNAL_SERVER_ERROR, "FCM500_2", "서버 에러, FCM 서버에 AccessToken 요청할 때 에러 발생."),
     FCM_SEND_MESSAGE_ERROR(INTERNAL_SERVER_ERROR    , "FCM500_3", "서버 에러, FCM 서버에 메시지를 전송할 때 에러 발생. FcmToken이 유효한지 확인해주세요."), ;
 
diff --git a/src/main/java/treehouse/server/global/fcm/service/FcmService.java b/src/main/java/treehouse/server/global/fcm/service/FcmService.java
index 4b33396..9595369 100644
--- a/src/main/java/treehouse/server/global/fcm/service/FcmService.java
+++ b/src/main/java/treehouse/server/global/fcm/service/FcmService.java
@@ -4,6 +4,7 @@
 import com.google.firebase.messaging.FirebaseMessagingException;
 import com.google.firebase.messaging.Message;
 import com.google.firebase.messaging.Notification;
+import lombok.AllArgsConstructor;
 import lombok.RequiredArgsConstructor;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -19,10 +20,11 @@
 import treehouse.server.global.fcm.dto.FCMDto;
 
 import java.util.List;
+import java.util.Optional;
 
 @Service
 @RequiredArgsConstructor
-@Transactional(readOnly = true)
+//@Transactional(readOnly = true)
 public class FcmService {
     Logger logger = LoggerFactory.getLogger(FcmService.class);
 
@@ -49,17 +51,20 @@ public void testFCMService(String fcmToken)
 
     @Transactional(readOnly = false)
     public UserResponseDTO.saveFcmToken saveFcmToken(User user, FCMDto.saveFcmTokenDto request) {
-        boolean isSuccess = false;
-        logger.error("토큰 값 : {}",request.getFcmToken());
-        if (fcmTokenRepository.existsByUserAndToken(user, request.getFcmToken())) {
-            throw new FcmException(GlobalErrorCode.FCM_ALREADY_EXISTS_TOKEN);
-        }else{
+        boolean isSuccess = true;
+        logger.info("토큰 값 : {}", request.getFcmToken());
+
+
+        // 한 user 당 가장 최신의 fcm token 값 하나만 db 에 저장하도록 수정
+        if (fcmTokenRepository.existsByUser(user)) {
+            FcmToken fcmToken = fcmTokenRepository.findByUser(user).orElseThrow(() -> new FcmException(GlobalErrorCode.FCM_TOKEN_NOT_EXISTS));
+            fcmToken.update(request.getFcmToken());
+        } else {
             fcmTokenRepository.save(FcmToken.builder()
                     .user(user)
                     .token(request.getFcmToken())
                     .build()
             );
-            isSuccess = true;
         }
         return UserMapper.toSaveFcmToken(user, isSuccess);
     }
@@ -67,30 +72,27 @@ public UserResponseDTO.saveFcmToken saveFcmToken(User user, FCMDto.saveFcmTokenD
 
     public void sendFcmMessage(User receiver, String title, String body) {
 
-        List<FcmToken> fcmTokenList = fcmTokenRepository.findAllByUser(receiver);
-        if (fcmTokenList.isEmpty()) {
-            return;
-        }
+        FcmToken fcmToken = fcmTokenRepository.findByUser(receiver).orElseThrow(() -> new FcmException(GlobalErrorCode.FCM_TOKEN_NOT_EXISTS));
 
-        for (FcmToken fcmToken : fcmTokenList) {
-            String token = fcmToken.getToken();
-            logger.info("전송하고자 하는 FCM 토큰 값 : " + token);
-            Message message = Message.builder()
-                    .setToken(token)
-                    .setNotification(
-                            Notification.builder()
-                                    .setTitle(title)
-                                    .setBody(body)
-                                    .build())
-                    .build();
-            try {
-                String response = FirebaseMessaging.getInstance().send(message);
-                logger.info("the response of request FCM : {}",response);
-            } catch (FirebaseMessagingException e) {
-                throw new FcmException(GlobalErrorCode.FCM_SEND_MESSAGE_ERROR);
-            }
-        }
+        String token = fcmToken.getToken();
+        logger.info("전송하고자 하는 FCM 토큰 값 : " + token);
+
+        Message message = Message.builder()
+                .setToken(token)
+                .setNotification(
+                        Notification.builder()
+                                .setTitle(title)
+                                .setBody(body)
+                                .build())
+                .build();
 
+        try {
+            String response = FirebaseMessaging.getInstance().send(message);
+            logger.info("the response of request FCM : {}",response);
+        } catch (FirebaseMessagingException e) {
+            logger.error("FCM 푸시 알림 전송 실패, 이유 : {}", e.getMessage());
+            throw new FcmException(GlobalErrorCode.FCM_SEND_MESSAGE_ERROR);
+        }
 
     }
 
@@ -98,4 +100,5 @@ public void sendFcmMessage(User receiver, String title, String body) {
     public void deleteAllFcmToken(User user) {
         fcmTokenRepository.deleteAllByUser(user);
     }
+
 }