diff --git a/lib/hako/application.rb b/lib/hako/application.rb
index 5ac1d65..3fde33e 100644
--- a/lib/hako/application.rb
+++ b/lib/hako/application.rb
@@ -15,7 +15,7 @@ class Application
     #   @return [Hash]
     attr_reader :id, :root_path, :definition
 
-    def initialize(definition_path, expand_variables: true, ask_keys: false)
+    def initialize(definition_path, expand_variables: true, ask_keys: false, ext_vars: {})
       path = Pathname.new(definition_path)
       @id = path.basename.sub_ext('').to_s
       @root_path = path.parent
@@ -24,7 +24,7 @@ def initialize(definition_path, expand_variables: true, ask_keys: false)
         when '.yml', '.yaml'
           YamlLoader.new.load(path)
         when '.jsonnet', '.json'
-          JsonnetLoader.new(self, expand_variables: expand_variables, ask_keys: ask_keys).load(path)
+          JsonnetLoader.new(self, expand_variables: expand_variables, ask_keys: ask_keys, ext_vars: ext_vars).load(path)
         else
           raise Error.new("Unknown extension: #{path}")
         end
diff --git a/lib/hako/cli.rb b/lib/hako/cli.rb
index 3e7faba..14108a8 100644
--- a/lib/hako/cli.rb
+++ b/lib/hako/cli.rb
@@ -73,6 +73,7 @@ def run(argv)
           else
             {}
           end
+        options.merge!(ext_vars: @ext_vars)
         Commander.new(Application.new(@definition_path, options)).deploy(force: @force, tag: @tag, dry_run: @dry_run, timeout: @timeout)
       end
 
@@ -83,6 +84,7 @@ def parse!(argv)
         @dry_run = false
         @verbose = false
         @timeout = DEFAULT_TIMEOUT
+        @ext_vars = {}
         parser.parse!(argv)
         @definition_path = argv.first
 
@@ -101,6 +103,10 @@ def parser
           opts.on('-n', '--dry-run', 'Enable dry-run mode') { @dry_run = true }
           opts.on('-v', '--verbose', 'Enable verbose logging') { @verbose = true }
           opts.on('--timeout=TIMEOUT_SEC', "Timeout deployment after TIMEOUT_SEC seconds (default: #{DEFAULT_TIMEOUT})") { |v| @timeout = v.to_i }
+          opts.on('--ext-var=KEY=VAL', 'Specify external variable for Jsonnet') do |arg|
+            k, v = arg.split('=', 2)
+            @ext_vars[k] = v
+          end
         end
       end
     end
@@ -121,12 +127,14 @@ def run(argv)
           else
             {}
           end
+        options.merge!(ext_vars: @ext_vars)
         Commander.new(Application.new(@definition_path, options)).rollback(dry_run: @dry_run)
       end
 
       def parse!(argv)
         @dry_run = false
         @verbose = false
+        @ext_vars = {}
         parser.parse!(argv)
         @definition_path = argv.first
 
@@ -142,6 +150,10 @@ def parser
           opts.version = VERSION
           opts.on('-n', '--dry-run', 'Enable dry-run mode') { @dry_run = true }
           opts.on('-v', '--verbose', 'Enable verbose logging') { @verbose = true }
+          opts.on('--ext-var=KEY=VAL', 'Specify external variable for Jsonnet') do |arg|
+            k, v = arg.split('=', 2)
+            @ext_vars[k] = v
+          end
         end
       end
     end
@@ -162,6 +174,7 @@ def run(argv)
           else
             {}
           end
+        options.merge!(ext_vars: @ext_vars)
         Commander.new(Application.new(@definition_path, options)).oneshot(@argv, tag: @tag, containers: @containers, env: @env, dry_run: @dry_run, no_wait: @no_wait)
       end
 
@@ -171,6 +184,7 @@ def parse!(argv)
         @env = {}
         @verbose = false
         @no_wait = false
+        @ext_vars = {}
         parser.parse!(argv)
         @definition_path = argv.shift
         @argv = argv
@@ -194,6 +208,10 @@ def parser
             k, v = arg.split('=', 2)
             @env[k] = v
           end
+          opts.on('--ext-var=KEY=VAL', 'Specify external variable for Jsonnet') do |arg|
+            k, v = arg.split('=', 2)
+            @ext_vars[k] = v
+          end
         end
       end
     end
@@ -202,12 +220,13 @@ class ShowDefinition
       def run(argv)
         parse!(argv)
         require 'hako/application'
-        app = Application.new(@path, expand_variables: @expand_variables)
+        app = Application.new(@path, expand_variables: @expand_variables, ext_vars: @ext_vars)
         puts JSON.pretty_generate(app.definition)
       end
 
       def parse!(argv)
         @expand_variables = false
+        @ext_vars = {}
         parser.parse!(argv)
         @path = argv.first
         if @path.nil?
@@ -221,6 +240,10 @@ def parser
           opts.banner = 'hako show-definition FILE'
           opts.version = VERSION
           opts.on('--expand', 'Expand variables (Jsonnet only)') { @expand_variables = true }
+          opts.on('--ext-var=KEY=VAL', 'Specify external variable for Jsonnet') do |arg|
+            k, v = arg.split('=', 2)
+            @ext_vars[k] = v
+          end
         end
       end
     end
@@ -230,10 +253,11 @@ def run(argv)
         parse!(argv)
         require 'hako/application'
         require 'hako/commander'
-        Commander.new(Application.new(@definition_path, expand_variables: false)).status
+        Commander.new(Application.new(@definition_path, expand_variables: false, ext_vars: @ext_vars)).status
       end
 
       def parse!(argv)
+        @ext_vars = {}
         parser.parse!(argv)
         @definition_path = argv.first
 
@@ -247,6 +271,10 @@ def parser
         @parser ||= OptionParser.new do |opts|
           opts.banner = 'hako status FILE'
           opts.version = VERSION
+          opts.on('--ext-var=KEY=VAL', 'Specify external variable for Jsonnet') do |arg|
+            k, v = arg.split('=', 2)
+            @ext_vars[k] = v
+          end
         end
       end
     end
@@ -257,11 +285,12 @@ def run(argv)
         require 'hako/application'
         require 'hako/commander'
 
-        Commander.new(Application.new(@definition_path, expand_variables: false)).remove(dry_run: @dry_run)
+        Commander.new(Application.new(@definition_path, expand_variables: false, ext_vars: @ext_vars)).remove(dry_run: @dry_run)
       end
 
       def parse!(argv)
         @dry_run = false
+        @ext_vars = {}
         parser.parse!(argv)
         @definition_path = argv.first
 
@@ -276,6 +305,10 @@ def parser
           opts.banner = 'hako remove FILE'
           opts.version = VERSION
           opts.on('-n', '--dry-run', 'Enable dry-run mode') { @dry_run = true }
+          opts.on('--ext-var=KEY=VAL', 'Specify external variable for Jsonnet') do |arg|
+            k, v = arg.split('=', 2)
+            @ext_vars[k] = v
+          end
         end
       end
     end
@@ -286,11 +319,12 @@ def run(argv)
         require 'hako/application'
         require 'hako/commander'
 
-        Commander.new(Application.new(@definition_path, expand_variables: false)).stop(dry_run: @dry_run)
+        Commander.new(Application.new(@definition_path, expand_variables: false, ext_vars: @ext_vars)).stop(dry_run: @dry_run)
       end
 
       def parse!(argv)
         @dry_run = false
+        @ext_vars = {}
         parser.parse!(argv)
         @definition_path = argv.first
 
@@ -305,6 +339,10 @@ def parser
           opts.banner = 'hako stop FILE'
           opts.version = VERSION
           opts.on('-n', '--dry-run', 'Enable dry-run mode') { @dry_run = true }
+          opts.on('--ext-var=KEY=VAL', 'Specify external variable for Jsonnet') do |arg|
+            k, v = arg.split('=', 2)
+            @ext_vars[k] = v
+          end
         end
       end
     end
diff --git a/lib/hako/jsonnet_loader.rb b/lib/hako/jsonnet_loader.rb
index 5400b4d..3cbeddc 100644
--- a/lib/hako/jsonnet_loader.rb
+++ b/lib/hako/jsonnet_loader.rb
@@ -12,11 +12,12 @@ class JsonnetLoader
     # @param [Application] application
     # @param [Boolean] expand_variables
     # @param [Boolean] ask_keys
-    def initialize(application, expand_variables:, ask_keys:)
+    def initialize(application, expand_variables:, ask_keys:, ext_vars:)
       @vm = Jsonnet::VM.new
       @root_path = application.root_path
       define_provider_functions(expand_variables, ask_keys)
       @vm.ext_var('appId', application.id)
+      ext_vars.each { |k, v| @vm.ext_var(k.to_s, v) }
     end
 
     # @param [Pathname] path
diff --git a/spec/fixtures/jsonnet/default_with_ext_var.jsonnet b/spec/fixtures/jsonnet/default_with_ext_var.jsonnet
new file mode 100644
index 0000000..53c7c62
--- /dev/null
+++ b/spec/fixtures/jsonnet/default_with_ext_var.jsonnet
@@ -0,0 +1,11 @@
+{
+  app: {
+    image: std.extVar('app_image'),
+  },
+  sidecars: {
+    front: {
+      type: 'nginx',
+      image_tag: std.extVar('front_image'),
+    },
+  },
+}
diff --git a/spec/hako/definition_loader_spec.rb b/spec/hako/definition_loader_spec.rb
index 46abda5..d926ece 100644
--- a/spec/hako/definition_loader_spec.rb
+++ b/spec/hako/definition_loader_spec.rb
@@ -63,5 +63,37 @@
         end
       end
     end
+
+    context 'with ext_vars' do
+      let(:fixture_name) { 'default_with_ext_var.jsonnet' }
+      let(:app) { Hako::Application.new(fixture_root.join('jsonnet', fixture_name), ext_vars: ext_vars) }
+
+      context 'specify ext_vars' do
+        let(:ext_vars) do
+          {
+            app_image: 'app-image',
+            front_image: 'front-image',
+          }
+        end
+
+        it 'loads all containers' do
+          containers = definition_loader.load
+          expect(containers.keys).to match_array(%w[app front])
+          expect(containers.values).to all(be_a(Hako::Container))
+          expect(containers['app'].image_tag).to eq('app-image:latest')
+          expect(containers['app'].links).to eq([])
+          expect(containers['front'].image_tag).to eq('front-image')
+          expect(containers['front'].links).to eq([])
+        end
+      end
+
+      context 'not specify ext_vars' do
+        let(:ext_vars) { {} }
+
+        it 'error occur' do
+          expect { definition_loader.load }.to raise_error(Jsonnet::EvaluationError)
+        end
+      end
+    end
   end
 end