diff --git a/lib/one_gadget.rb b/lib/one_gadget.rb
index abb5f728..4b1ebf83 100644
--- a/lib/one_gadget.rb
+++ b/lib/one_gadget.rb
@@ -67,6 +67,9 @@ def one_gadget(arg = nil, **options)
   OneGadget.gadgets(**options)
 end
 
+require 'one_gadget/update'
+OneGadget::Update.check!
+
 require 'one_gadget/fetcher'
 require 'one_gadget/helper'
 require 'one_gadget/logger'
diff --git a/lib/one_gadget/logger.rb b/lib/one_gadget/logger.rb
index d6964c19..2b3abb6d 100644
--- a/lib/one_gadget/logger.rb
+++ b/lib/one_gadget/logger.rb
@@ -10,7 +10,7 @@ module Logger
       prep = ' ' * 12
       message = msg.lines.map.with_index do |str, i|
         next str if i.zero?
-        prep + str
+        str.strip.empty? ? str : prep + str
       end
       color = case severity
               when 'WARN' then :warn
diff --git a/lib/one_gadget/update.rb b/lib/one_gadget/update.rb
new file mode 100644
index 00000000..adfa649b
--- /dev/null
+++ b/lib/one_gadget/update.rb
@@ -0,0 +1,59 @@
+require 'fileutils'
+
+require 'one_gadget/helper'
+require 'one_gadget/logger'
+
+module OneGadget
+  # For automatically check update.
+  module Update
+    # At least 7 days between check for new version.
+    FREQUENCY = 7 * 24 * 60 * 60
+    # Path to cache file.
+    CACHE_FILE = File.join(ENV['HOME'], '.cache', 'one_gadget', 'update').freeze
+
+    class << self
+      # Check if new releases have been drafted.
+      #
+      # @return [void]
+      def check!
+        return unless need_check?
+        OneGadget::Logger.info("Checking for new versions of OneGadget\n" \
+                               "To disable this functionality, do\n$ echo never > #{CACHE_FILE}\n\n")
+        latest = Helper.latest_tag[1..-1] # remove 'v'
+        if Gem::Version.new(latest) <= Gem::Version.new(OneGadget::VERSION)
+          return OneGadget::Logger.info("You have the latest version of OneGadget (#{latest})!\n\n")
+        end
+
+        # show update message
+        msg = format("A newer version of OneGadget is available (%s --> %s).\n", OneGadget::VERSION, latest)
+        msg << "Update with: $ gem update one_gadget\n\n"
+        OneGadget::Logger.info(msg)
+      end
+
+      private
+
+      # check ~/.cache/one_gadget/update
+      def need_check?
+        cache = cache_file
+        return false if cache.nil? # cache file fails, no update check.
+        return false if IO.binread(cache).strip == 'never'
+        Time.now >= last_check + FREQUENCY
+      end
+
+      def last_check
+        cache = cache_file
+        return Time.now if cache.nil?
+        File.open(cache, &:mtime)
+      end
+
+      def cache_file
+        dir = File.dirname(CACHE_FILE)
+        FileUtils.mkdir_p(dir) unless File.directory?(dir)
+        IO.binwrite(CACHE_FILE, '') unless File.exist?(CACHE_FILE)
+        CACHE_FILE
+      rescue # prevent dir is not writable
+        return nil
+      end
+    end
+  end
+end
diff --git a/spec/update_spec.rb b/spec/update_spec.rb
new file mode 100644
index 00000000..d46658a9
--- /dev/null
+++ b/spec/update_spec.rb
@@ -0,0 +1,70 @@
+require 'logger'
+
+require 'one_gadget/update'
+require 'one_gadget/version'
+
+describe OneGadget::Update do
+  before(:all) do
+    # precent fail on CI
+    @hook_cache_file = lambda do |&block|
+      tmp = Dir::Tmpname.make_tmpname('/tmp/one_gadget/update', nil)
+      stub_const('OneGadget::Update::CACHE_FILE', tmp)
+      block.call(tmp)
+    end
+
+    @hook_logger = lambda do |&block|
+      # no method 'reopen' before ruby 2.3
+      org_logger = OneGadget::Logger.instance_variable_get(:@logger)
+      new_logger = ::Logger.new($stdout)
+      new_logger.formatter = org_logger.formatter
+      OneGadget::Logger.instance_variable_set(:@logger, new_logger)
+      block.call
+      OneGadget::Logger.instance_variable_set(:@logger, org_logger)
+    end
+  end
+
+  after(:all) do
+    FileUtils.rm_r('/tmp/one_gadget')
+  end
+
+  it 'cache_file' do
+    skip 'Windows so hard' unless RUBY_PLATFORM =~ /linux/
+    @hook_cache_file.call do |path|
+      expect(described_class.send(:cache_file)).to eq path
+      File.chmod(0o000, File.dirname(path))
+      expect(described_class.send(:cache_file)).to be nil
+      File.chmod(0o700, File.dirname(path))
+    end
+  end
+
+  it 'need_check?' do
+    @hook_cache_file.call do |path|
+      expect(described_class.send(:need_check?)).to be false
+      now = Time.now
+      allow(Time).to receive(:now).and_return(now + 7 * 24 * 3600)
+      expect(described_class.send(:need_check?)).to be true
+      IO.binwrite(path, 'never')
+      expect(described_class.send(:need_check?)).to be false
+    end
+  end
+
+  it 'check!' do
+    OneGadget::Helper.color_off!
+    @hook_cache_file.call do |path|
+      allow(described_class).to receive(:need_check?).and_return(true)
+      expect { @hook_logger.call { described_class.check! } }.to output(<<-EOS).to_stdout
+[OneGadget] Checking for new versions of OneGadget
+            To disable this functionality, do
+            $ echo never > #{path}
+
+[OneGadget] You have the latest version of OneGadget (#{OneGadget::VERSION})!
+
+      EOS
+      stub_const('OneGadget::VERSION', '0.0.0')
+      expect { @hook_logger.call { described_class.check! } }.to output(include(<<-EOS)).to_stdout
+$ gem update one_gadget
+      EOS
+    end
+    OneGadget::Helper.color_on!
+  end
+end