diff --git a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
index 22ee382..38d8fa5 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
@@ -56,15 +56,8 @@
      * @param month 月
      * @return そのアカウントの本に所属するtodoのうち、指定した年月のtodoを返します
      */
-    public HashMap<Integer, Todo> getTodosByMonth(String accountId, int bookId, int year, int month, String token){
-        HashMap<Integer, Todo> result = new HashMap<>();
-        var yearMonthMap = todos.get(accountId).get(bookId).get(year).get(month);
-        for(var dayValues : yearMonthMap.values()){
-            for(int todoId : dayValues.keySet()){
-                result.put(todoId, dayValues.get(todoId));
-            }
-        }
-        return result;
+    public HashMap<Integer, HashMap<Integer, Todo>> getTodosByMonth(String accountId, int bookId, int year, int month, String token){
+        return todos.get(accountId).get(bookId).get(year).get(month);
     }
 
     /**
@@ -75,7 +68,7 @@
      * @param yearMonth 年月を-で区切った文字列(yyyy-mm)
      * @return そのアカウントの本に所属するtodoのうち、指定した年月のtodoを返します
      */
-    public HashMap<Integer, Todo> getTodosByMonth(String accountId, int bookId, String yearMonth, String token){
+    public HashMap<Integer, HashMap<Integer, Todo>> getTodosByMonth(String accountId, int bookId, String yearMonth, String token){
         String[] yearMonths = yearMonth.split("-");
         int year = Integer.parseInt(yearMonths[0]);
         int month = Integer.parseInt(yearMonths[1]);