diff --git a/README.md b/README.md
index f103e61..0cb1086 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 [![License](https://poser.pugx.org/billplz/billplz-api/license)](https://packagist.org/packages/billplz/billplz-api)
 
 ## Minimum System Requirement
-- PHP 5.6 or newer
+- PHP 7.0 or newer
 
 ## Installation
 
diff --git a/composer.json b/composer.json
index 38dca75..9704524 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
     ],
     "minimum-stability": "dev",
     "require": {
-        "php": ">=5.6"
+        "php": ">=7.0"
     },
     "suggest": {
         "guzzlehttp/guzzle": "HTTP Client Library ~6.0"
diff --git a/composer.lock b/composer.lock
index 680f28f..e00c697 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "content-hash": "a54fa3f102bbb73b66857e381ecae397",
+    "content-hash": "63b3a95f0b9a6aae07f887cb518537a3",
     "packages": [],
     "packages-dev": [],
     "aliases": [],
@@ -13,7 +13,7 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": ">=5.6"
+        "php": ">=7.0"
     },
     "platform-dev": []
 }