diff --git a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
index 550e06a..cb143f2 100644
--- a/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
+++ b/src/main/java/org/ntlab/citrusserver/repositories/TodoManager.java
@@ -31,8 +31,11 @@
 
     private final AccountManager accountManager;
 
-    public TodoManager(AccountManager accountManager) {
+    private final BookManager bookManager;
+
+    public TodoManager(AccountManager accountManager, BookManager bookManager) {
         this.accountManager = accountManager;
+        this.bookManager = bookManager;
     }
 
     /**
@@ -69,15 +72,16 @@
      * @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, HashMap<Integer, Todo>> getTodosByMonth(String accountId, int bookId, int year, int month, String token){
+        if(!accountManager.checkToken(accountId, token)){
+            return null;
+        }
+
         if(!todos.get(accountId).get(bookId).containsKey(year)){
             return new HashMap<Integer, HashMap<Integer, Todo>>();
         }
         if(!todos.get(accountId).get(bookId).get(year).containsKey(month)){
             return new HashMap<Integer, HashMap<Integer, Todo>>();
         }
-        if(!accountManager.checkToken(accountId, token)){
-            return null;
-        }
         return todos.get(accountId).get(bookId).get(year).get(month);
     }
 
@@ -189,6 +193,9 @@
         if(!accountManager.checkToken(accountId, token)){
             return -1;
         }
+        if(!bookManager.getBooks(accountId).containsKey(bookId)){
+            return -1;
+        }
         if(!todos.containsKey(accountId)){
             todos.put(accountId, new HashMap<>());
         }
@@ -245,6 +252,24 @@
         if(!accountManager.checkToken(accountId, token)){
             return;
         }
+        if(!todos.containsKey(accountId)){
+            return;
+        }
+        if(!todos.get(accountId).containsKey(bookId)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).containsKey(year)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).get(year).containsKey(month)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).get(year).get(month).containsKey(day)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).get(year).get(month).get(day).containsKey(todoId)){
+            return;
+        }
         todos.get(accountId).get(bookId).get(year).get(month).get(day).remove(todoId);
     }
 
@@ -276,6 +301,27 @@
         if(!accountManager.checkToken(accountId, token)){
             return;
         }
+        if(!accountManager.checkToken(accountId, token)){
+            return;
+        }
+        if(!todos.containsKey(accountId)){
+            return;
+        }
+        if(!todos.get(accountId).containsKey(bookId)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).containsKey(year)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).get(year).containsKey(month)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).get(year).get(month).containsKey(day)){
+            return;
+        }
+        if(!todos.get(accountId).get(bookId).get(year).get(month).get(day).containsKey(todoId)){
+            return;
+        }
         todos.get(accountId).get(bookId).get(year).get(month).get(day).get(todoId).setCheck(check);
     }