diff --git a/src/main/java/org/ntlab/citrusserver/resources/BooksRest.java b/src/main/java/org/ntlab/citrusserver/resources/BooksRest.java
index fe0dea4..2e271cb 100644
--- a/src/main/java/org/ntlab/citrusserver/resources/BooksRest.java
+++ b/src/main/java/org/ntlab/citrusserver/resources/BooksRest.java
@@ -36,7 +36,8 @@
     @Produces(MediaType.APPLICATION_JSON)
     public  HashMap<Integer, Book> getBooks(@PathParam("account_id") String account_id, @QueryParam("token") String token){
 
-        if(bookManager.getBooks(account_id) == null){
+        HashMap<Integer, Book> books = bookManager.getBooks(account_id);
+        if(books == null){
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -46,7 +47,7 @@
                 throw new WebApplicationException(response.build());
             }
             else{
-                return bookManager.getBooks(account_id);
+                return books;
             }
         }
     }
@@ -57,7 +58,8 @@
     @Consumes(MediaType.APPLICATION_FORM_URLENCODED)  // postmanのbodyに入力する値がある時
     public Book createBook(@PathParam("account_id") String account_id, @FormParam("title") String title, @FormParam("color") String color, @FormParam("publicity") Boolean publicity, @FormParam("token") String token) {
 
-        if (bookManager.createBook(account_id, title, color, publicity) == null){
+        Book book = bookManager.createBook(account_id, title, color, publicity);
+        if (book == null){
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -80,7 +82,8 @@
     @Produces(MediaType.APPLICATION_JSON)
     public Book getBook(@PathParam("account_id") String account_id, @PathParam("book_id") Integer book_id, @QueryParam("token") String token){
 
-        if (bookManager.getBook(account_id, book_id) == null){
+        Book book = bookManager.getBook(account_id, book_id);
+        if (book == null){
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -90,7 +93,7 @@
                 throw new WebApplicationException(response.build());
             }
             else{
-                return bookManager.getBook(account_id, book_id);
+                return book;
             }
         }
     }
@@ -101,7 +104,8 @@
     @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
     public String deleteBook(@PathParam("account_id") String account_id, @PathParam("book_id") Integer book_id, @QueryParam("token") String token){
 
-        if(bookManager.deleteBook(account_id, book_id) == -1){
+        int check = bookManager.deleteBook(account_id, book_id);
+        if(check == -1){
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -123,7 +127,8 @@
     @Produces(MediaType.TEXT_PLAIN)
     public String getTitle(@PathParam("account_id") String account_id, @PathParam("book_id") Integer book_id, @QueryParam("token") String token){
 
-        if (bookManager.getTitle(account_id, book_id) == null) {
+        String str = bookManager.getTitle(account_id, book_id);
+        if (str == null) {
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -133,7 +138,7 @@
                 throw new WebApplicationException(response.build());
             }
             else{
-                return (bookManager.getTitle(account_id, book_id));
+                return str;
             }
         }
     }
@@ -145,7 +150,8 @@
     @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
     public String putTitle(@PathParam("account_id") String account_id, @PathParam("book_id") Integer book_id, @FormParam("title") String title, @FormParam("token") String token){
 
-        if(bookManager.putTitle(account_id, book_id, title) == -1){
+        int check = bookManager.putTitle(account_id, book_id, title);
+        if(check == -1){
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -167,7 +173,8 @@
     @Produces(MediaType.TEXT_PLAIN)
     public Boolean getPublicity(@PathParam("account_id") String account_id, @PathParam("book_id") Integer book_id, @QueryParam("token") String token){
 
-        if (bookManager.getPublicity(account_id, book_id) == null) {
+        Boolean publicity = bookManager.getPublicity(account_id, book_id);
+        if (publicity == null) {
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -177,7 +184,7 @@
                 throw new WebApplicationException(response.build());
             }
             else{
-                return bookManager.getPublicity(account_id, book_id);
+                return publicity;
             }
         }
     }
@@ -188,7 +195,9 @@
     @Produces(MediaType.TEXT_PLAIN)
     @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
     public String putPublicity(@PathParam("account_id") String account_id, @PathParam("book_id") Integer book_id, @FormParam("publicity") Boolean publicity, @FormParam("token") String token){
-        if(bookManager.putPublicity(account_id, book_id, publicity) == -1){
+
+        int check = bookManager.putPublicity(account_id, book_id, publicity);
+        if(check == -1){
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }
@@ -209,7 +218,9 @@
     @PUT
     @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
     public String putColor(@PathParam("account_id") String account_id, @PathParam("book_id") Integer book_id, @FormParam("color") String color, @FormParam("token") String token){
-        if(bookManager.putColor(account_id, book_id, color) == -1){
+
+        int check = bookManager.putColor(account_id, book_id, color);
+        if(check == -1){
             var response = Response.status(Response.Status.NOT_FOUND).entity("アカウントが見つかりません");
             throw new WebApplicationException(response.build());
         }