diff --git a/Gemfile b/Gemfile
index 31e2272..9f699e2 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.2.2'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # Use Puma as the app server
-gem 'puma', '~> 3.12'
+gem 'puma', '~> 4.3'
 # JSONの出力 Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
 gem 'jbuilder', '~> 2.5'
 # Use Redis adapter to run Action Cable in production
diff --git a/Gemfile.lock b/Gemfile.lock
index 9b0b5b3..d8858d9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -94,7 +94,9 @@ GEM
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
     method_source (0.9.2)
-    mimemagic (0.3.2)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.1)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
@@ -111,7 +113,8 @@ GEM
       method_source (~> 0.9.0)
     pry-rails (0.3.8)
       pry (>= 0.10.4)
-    puma (3.12.4)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -200,7 +203,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
   pry-rails
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (~> 5.2.2)
   rspec-rails
   rspec_junit_formatter