diff --git a/composer.json b/composer.json
index 36263d77..f9ed47fe 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
   "require": {
     "php": "^8.2",
     "composer-runtime-api": "^2.0",
-    "guzzlehttp/guzzle": "^7.3",
+    "guzzlehttp/guzzle": "^8.0",
     "guzzlehttp/psr7": "^1.7 || ^2.0 || ^3.0"
   },
   "require-dev": {
diff --git a/examples/EchoBot/composer.json b/examples/EchoBot/composer.json
index cabd54da..8a612811 100644
--- a/examples/EchoBot/composer.json
+++ b/examples/EchoBot/composer.json
@@ -32,7 +32,7 @@
     "slim/psr7": "^1.6",
     "slim/http": "^1.3",
     "monolog/monolog": "^3.0.0",
-    "guzzlehttp/guzzle": "^7.5",
+    "guzzlehttp/guzzle": "^8.0",
     "guzzlehttp/psr7": "^3.0",
     "php-di/slim-bridge": "^3.3",
     "linecorp/line-bot-sdk": "*"
diff --git a/examples/KitchenSink/composer.json b/examples/KitchenSink/composer.json
index 5ae7a1d9..9b656aed 100644
--- a/examples/KitchenSink/composer.json
+++ b/examples/KitchenSink/composer.json
@@ -32,7 +32,7 @@
     "slim/psr7": "^1.6",
     "slim/http": "^1.3",
     "monolog/monolog": "^3.0.0",
-    "guzzlehttp/guzzle": "^7.5",
+    "guzzlehttp/guzzle": "^8.0",
     "guzzlehttp/psr7": "^3.0",
     "php-di/slim-bridge": "^3.3",
     "linecorp/line-bot-sdk": "*"