diff --git a/main.py b/main.py
index 3a637ff..1179a96 100644
--- a/main.py
+++ b/main.py
@@ -1,4 +1,3 @@
-import codecs
 import io
 import json
 import zipfile
@@ -27,6 +26,12 @@
         del i['source']
         ndc9_items[key] = i
 
+with open('./templates/index.html', encoding='utf-8') as file:
+    index_html = file.read()
+
+with open('jsonschema.json', encoding='utf-8') as file:
+    json_schema = json.load(file)
+
 
 @app.get(
     '/',
@@ -37,8 +42,7 @@
     response_class=HTMLResponse,
 )
 async def index():
-    with codecs.open('./templates/index.html', 'r', 'utf-8') as file:
-        return file.read()
+    return index_html
 
 
 @app.get(
@@ -49,8 +53,6 @@ async def index():
     response_description='JSONスキーマを返す',
 )
 async def schema():
-    with codecs.open('jsonschema.json', 'r', 'utf-8') as file:
-        json_schema = json.load(file)
     return ORJSONResponse(json_schema, headers={'Access-Control-Allow-Origin': '*'})
 
 
diff --git a/validate.py b/validate.py
index fb1ae24..213bf0f 100644
--- a/validate.py
+++ b/validate.py
@@ -1,4 +1,3 @@
-import codecs
 import json
 
 import jsonschema
@@ -8,7 +7,7 @@
     url = 'http://127.0.0.1:8000/ndc9.json'
     r = requests.get(url, headers={'content-type': 'application/json'})
     data = r.json()
-    with codecs.open('jsonschema.json', 'r', 'utf-8') as file:
+    with open('jsonschema.json', encoding='utf-8') as file:
         json_schema = json.load(file)
         for item in data.values():
             jsonschema.validate(item, json_schema)