diff --git a/cookbooks/prometheus/install.rb b/cookbooks/prometheus/install.rb
index a1441bc..3891116 100644
--- a/cookbooks/prometheus/install.rb
+++ b/cookbooks/prometheus/install.rb
@@ -1,6 +1,9 @@
 prometheus_url = ''
 prometheus_bin = ''
 
+vtag           = ''
+tag            = ''
+
 # Calculate the Download URL:
 begin
   require 'net/http'
@@ -22,28 +25,33 @@ rescue
   raise 'Cannot connect to http://github.com.'
 end
 
-# Download:
-TMP = "/tmp/#{prometheus_bin}"
 
-execute "wget #{prometheus_url} -O #{TMP}"
+# バージョン確認して、アップデート必要かどうか確認
+result = run_command("prometheus --version 2>&1 | grep #{tag}", error: false)
+if result.exit_status != 0
+  # Download:
+  TMP = "/tmp/#{prometheus_bin}"
 
-# Install:
-directory node['prometheus']['storage'] do
-  owner 'root'
-  group 'root'
-  mode '755'
-end
-
-execute "tar zxf #{TMP} -C #{node['prometheus']['storage']} --strip-components 1"
-
-# Change Owner and Permissions:
-file "#{node['prometheus']['storage']}prometheus" do
-  owner 'root'
-  group 'root'
-  mode  '755'
-end
-
-# Create Link
-link "#{node['prometheus']['location']}prometheus" do
-  to "#{node['prometheus']['storage']}prometheus"
+  execute "wget #{prometheus_url} -O #{TMP}"
+
+  # Install:
+  directory node['prometheus']['storage'] do
+    owner 'root'
+    group 'root'
+    mode '755'
+  end
+
+  execute "tar zxf #{TMP} -C #{node['prometheus']['storage']} --strip-components 1"
+
+  # Change Owner and Permissions:
+  file "#{node['prometheus']['storage']}prometheus" do
+    owner 'root'
+    group 'root'
+    mode  '755'
+  end
+
+  # Create Link
+  link "#{node['prometheus']['location']}prometheus" do
+    to "#{node['prometheus']['storage']}prometheus"
+  end
 end