diff --git a/src/main/java/com/example/cosmos_serversb/models/Groups.java b/src/main/java/com/example/cosmos_serversb/models/Groups.java
index 757ada5..cc6756c 100644
--- a/src/main/java/com/example/cosmos_serversb/models/Groups.java
+++ b/src/main/java/com/example/cosmos_serversb/models/Groups.java
@@ -166,7 +166,7 @@
     }
 
     public static Request addRequests(String gId, String uId, String product, String deadline, int location){
-        if(product == null){
+        if(product == null || uId == null){
             return null; //not-null制約
         }
         String rId = getInstance().createRId();
diff --git a/src/main/java/com/example/cosmos_serversb/models/Users.java b/src/main/java/com/example/cosmos_serversb/models/Users.java
index 773355f..d6918bb 100644
--- a/src/main/java/com/example/cosmos_serversb/models/Users.java
+++ b/src/main/java/com/example/cosmos_serversb/models/Users.java
@@ -149,12 +149,23 @@
 
     public static DeleteResult deleteUser(String uId) {
         Session session = SessionManager.getInstance().getSession();
-        User deleteUser = (User) session.load(User.class, uId);
+        User deleteUser = (User) session.get(User.class, uId);
         if(deleteUser != null){
+            for(Group group : deleteUser.getGroups()){
+                if(group.getMembers().size() == 1){
+                    //グループにユーザが存在しなくなるため、グループごと削除する。
+                    Groups.getInstance().deleteGroup(group.getgId());
+                }else{
+                    //該当ユーザをグループから退会。
+                    group.deleteMember(deleteUser);
+                }
+            }
+            deleteUser.groups.clear();
             session.delete(deleteUser);
             System.out.println("massage: Already Deleted");
+            return DeleteResult.SUCCESS;
         }
-        return DeleteResult.SUCCESS;
+        return DeleteResult.FAILURE;
     }
 
     public static Token login(String uId,String pw) {