diff --git a/src/main/java/com/example/demo/controller/BookInsertController.java b/src/main/java/com/example/demo/controller/BookInsertController.java
index c725330..e3d5b2f 100644
--- a/src/main/java/com/example/demo/controller/BookInsertController.java
+++ b/src/main/java/com/example/demo/controller/BookInsertController.java
@@ -5,6 +5,8 @@ import java.util.ArrayList;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
+import org.springframework.validation.BindingResult;
+import org.springframework.validation.annotation.Validated;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 
@@ -42,19 +44,37 @@ private StorageLocationRepository storageLocationRepository;
 	    
 	    // 確認画面から戻る: POSTされた入力中の値がformに入ったまま入力画面へ
 	    @PostMapping("/bookInsertConfirm")
-	    public String bookInsertConfirm(BookInsert bookInsert,Model model) {
+	    public String bookInsertConfirm(@Validated BookInsert bookInsert,BindingResult result,Model model) {
+	    	if(result.hasErrors()) {
+	    		model.addAttribute("categoryList",categoryRepository.findAll());
+	    		if(bookInsert.getBookCategoryId() != null) { //nullじゃなかったら
+	    			model.addAttribute("subCategoryList",subCategoryRepository.findByBookCategory_BookCategoryId(bookInsert.getBookCategoryId()));
+	    			//そのカテゴリに属するサブカテゴリを持ってくる
+	    			} else{
+	    			model.addAttribute("subCategoryList",new ArrayList<>());
+	    			}
+	    		model.addAttribute("locationList",storageLocationRepository.findAll());
+	    		model.addAttribute("bookInsert", bookInsert);
+	    		return "bookInsert";
+	    		
+	    	}
 	    	System.out.println(bookInsert);
 	    	bookInsertService.save(bookInsert);
 	    	model.addAttribute("bookInsert",bookInsert);
 	        return "bookInsertConfirm";
 	    }
 	    
+	    //確認画面から「もどる」ボタンを押したら入力画面に戻る
 	    @PostMapping("/bookInsert")
 	    public String bookInsertBack(BookInsert bookInsert,Model model) {
 	    	model.addAttribute("categoryList",categoryRepository.findAll());
-	    	model.addAttribute("subCategoryList",new ArrayList<>());
-	    	model.addAttribute("locationList",storageLocationRepository.findAll());
-	    	model.addAttribute("bookInsert",bookInsert);
+	    	if(bookInsert.getBookCategoryId() != null) {
+	    		model.addAttribute("subCategoryList",subCategoryRepository.findByBookCategory_BookCategoryId(bookInsert.getBookCategoryId()));
+	    			} else{
+	    				model.addAttribute("subCategoryList",new ArrayList<>());
+	    			}
+	    		model.addAttribute("locationList",storageLocationRepository.findAll());
+	    		model.addAttribute("bookInsert",bookInsert);
 	        return "bookInsert";
 	    }
 	    
@@ -62,8 +82,7 @@ private StorageLocationRepository storageLocationRepository;
 	    public String changeCategory(BookInsert bookInsert,Model model) {
 	    	    //カテゴリプルダウンに表示するデータを取得
 	    		model.addAttribute("categoryList",categoryRepository.findAll());
-
-	        model.addAttribute("subCategoryList",subCategoryRepository.findByBookCategory_BookCategoryId(bookInsert.getBookCategoryId()));
+	    		model.addAttribute("subCategoryList",subCategoryRepository.findByBookCategory_BookCategoryId(bookInsert.getBookCategoryId()));
 	        model.addAttribute("locationList",storageLocationRepository.findAll());
 	        model.addAttribute("bookInsert", bookInsert);
 
diff --git a/src/main/java/com/example/demo/entity/BookInsert.java b/src/main/java/com/example/demo/entity/BookInsert.java
index 9305b62..be1fd47 100644
--- a/src/main/java/com/example/demo/entity/BookInsert.java
+++ b/src/main/java/com/example/demo/entity/BookInsert.java
@@ -8,6 +8,7 @@ import jakarta.persistence.GenerationType;
 import jakarta.persistence.Id;
 import jakarta.persistence.Table;
 import jakarta.persistence.Transient;
+import jakarta.validation.constraints.Pattern;
 
 import lombok.Data;
 
@@ -27,6 +28,8 @@ public class BookInsert {
     @Column(name = "title")
     private String title;
     
+    @Pattern(regexp = "^(?=(?:.*-){4})[0-9-]{17}$",
+    		message = "ISBNは半角数字(13文字)とハイフン(4つ)を含めて入力してください")
     @Column(name = "isbn")
     private String isbn;
     
diff --git a/src/main/resources/templates/bookInsert.html b/src/main/resources/templates/bookInsert.html
index 04a99d9..be4be18 100644
--- a/src/main/resources/templates/bookInsert.html
+++ b/src/main/resources/templates/bookInsert.html
@@ -26,7 +26,9 @@
 	<br><br>
 	
 	<label for="isbn">ISBN<span style="color:red;">※</span></label><br>
-	<input type="text" id="isbn" name="isbn" placeholder="例:978-1-23-456789-0" th:value="${bookInsert.isbn}" required>
+	<input type="text" id="isbn" name="isbn" placeholder="ISBNを入力" th:value="${bookInsert.isbn}"  required>
+		   <div th:if="${#fields.hasErrors('isbn')}" th:errors="*{isbn}" style="color:red">
+		   </div>
 		<br><br>
 	
 		<label for="title">著者名<span style="color:red;">※</span></label><br>
@@ -69,7 +71,7 @@
 		<br><br>
 		
 		<label for="condition">図書状態<span style="color:red;">※</span></label><br>
-		<select name="condition" required>
+		<select th:field="*{condition}" required>
 			<option value="">選択してください</option>
 		    <option value="1">新品同様</option>
 		    <option value="2">良好</option>
diff --git a/src/main/resources/templates/bookInsertConfirm.html b/src/main/resources/templates/bookInsertConfirm.html
index 9a53f47..882221c 100644
--- a/src/main/resources/templates/bookInsertConfirm.html
+++ b/src/main/resources/templates/bookInsertConfirm.html
@@ -17,7 +17,7 @@
 		    <input type="hidden" name="title" th:value="${bookInsert.title}">
 			<input type="hidden" name="isbn" th:value="${bookInsert.isbn}">
 			<input type="hidden" name="author" th:value="${bookInsert.author}">
-			<input type="hidden" name="category" th:value="${bookInsert.bookCategoryId}">
+			<input type="hidden" name="bookCategoryId" th:value="${bookInsert.bookCategoryId}">
 			<input type="hidden" name="subcategory" th:value="${bookInsert.subcategory}">
 			<input type="hidden" name="publisher" th:value="${bookInsert.publisher}">
 			<input type="hidden" name="publicationDate" th:value="${bookInsert.publicationDate}">