diff --git a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
index 22a2480..b3a1fa5 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
@@ -189,12 +189,12 @@
      * @param title 追加するべきtodoのタイトル
      * @return 新しいtodoのid
      */
-    public int createTodo(String accountId, int bookId, int year, int month, int day, String title, String token){
+    public Todo createTodo(String accountId, int bookId, int year, int month, int day, String title, String token){
         if(!accountManager.checkToken(accountId, token)){
-            return -1;
+            return null;
         }
         if(!bookManager.getBooks(accountId, token).containsKey(bookId)){
-            return -1;
+            return null;
         }
         if(!todos.containsKey(accountId)){
             todos.put(accountId, new HashMap<>());
@@ -221,7 +221,7 @@
         Todo newTodo = new Todo(title, false, year, month, day, newTodoId);
         todos.get(accountId).get(bookId).get(year).get(month).get(day).put(newTodoId, newTodo);
         nextTodoId.put(accountBook, newTodoId + 1);
-        return newTodoId;
+        return newTodo;
     }
 
     /**
@@ -233,7 +233,7 @@
      * @param title 追加したいtodoのタイトル
      * @return 新しいtodoのid
      */
-    public int createTodo(String accountId, int bookId, String yearMonthDay, String title, String token){
+    public Todo createTodo(String accountId, int bookId, String yearMonthDay, String title, String token){
         String[] yearMonthDays = yearMonthDay.split("-");
         int year = Integer.parseInt(yearMonthDays[0]);
         int month = Integer.parseInt(yearMonthDays[1]);