diff --git a/gulpfile.js b/gulpfile.js
index 0f1fb132..f3ea772c 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -130,7 +130,7 @@ gulp.task('clean_test_cache_server', () => del(TEST_CACHE_SERVER));
  */
 gulp.task('build', ['lint', 'build_dist_client', 'build_dist_server', 'build_dist_style', 'build_dist_legacy_lib']);
 
-gulp.task('build_dist_client', ['clean_dist_client', 'build_obj_client', 'build_obj_lib'], function () {
+gulp.task('build_dist_client', ['clean_dist_client', 'build_obj_client', 'build_obj_lib', 'build_dist_legacy_lib'], function () {
     const root = './karen.js';
     const ENTRY_POINT = path.resolve(OBJ_CLIENT, root);
 
diff --git a/package.json b/package.json
index ab42d885..05f9ea49 100644
--- a/package.json
+++ b/package.json
@@ -21,6 +21,7 @@
     "build_production": "cross-env NODE_ENV=production npm run build",
     "build_development": "cross-env NODE_ENV=development npm run build",
     "build": "gulp build",
+    "rollup": "cross-env ENABLE_ROLLUP=1 npm run gulp -- build_dist_client",
     "test": "gulp test",
     "gulp": "gulp"
   },
@@ -78,6 +79,7 @@
     "babel-cli": "^6.14.0",
     "babel-core": "^6.14.0",
     "babel-loader": "^6.2.5",
+    "babel-plugin-external-helpers": "^6.8.0",
     "babel-plugin-transform-es2015-modules-commonjs": "^6.14.0",
     "babel-plugin-transform-inline-environment-variables": "^6.8.0",
     "babel-plugin-transform-node-env-inline": "^6.8.0",
@@ -101,6 +103,11 @@
     "postcss-cli": "^2.6.0",
     "postcss-custom-properties": "^5.0.1",
     "postcss-import": "^8.1.2",
+    "rollup": "^0.35.14",
+    "rollup-plugin-babel": "^2.6.1",
+    "rollup-plugin-commonjs": "^5.0.3",
+    "rollup-plugin-node-globals": "^1.0.7",
+    "rollup-plugin-node-resolve": "^2.0.0",
     "stylelint": "^7.2.0",
     "tslint": "3.15.0-dev.0",
     "typescript": "2.1.0-dev.20160918",
diff --git a/rollup.config.js b/rollup.config.js
new file mode 100644
index 00000000..cee3582b
--- /dev/null
+++ b/rollup.config.js
@@ -0,0 +1,100 @@
+/// <reference path='./typings/index.d.ts'/>
+
+'use strict';
+
+const assert = require('assert');
+const path = require('path');
+
+const nodeResolve = require('rollup-plugin-node-resolve');
+const commonjs = require('rollup-plugin-commonjs');
+const babel = require('rollup-plugin-babel');
+const nodeGlobals = require('rollup-plugin-node-globals');
+
+const isRelease = process.env.NODE_ENV === 'production';
+
+const KAREN_ENTRY_POINT = process.env.KAREN_ENTRY_POINT;
+assert.ok(!!KAREN_ENTRY_POINT, 'not found process.env.KAREN_ENTRY_POINT');
+
+const KAREN_CLIENT_DIST_DIR = process.env.KAREN_CLIENT_DIST_DIR;
+assert.ok(!!KAREN_CLIENT_DIST_DIR, 'not found process.env.KAREN_CLIENT_DIST_DIR');
+
+const babelPresets = [
+];
+
+let babelPlugins = [
+    // For our target browsers, we need not some transforms.
+
+    // es2016 level
+    'babel-plugin-transform-exponentiation-operator',
+    // es2017 level
+    'babel-plugin-syntax-trailing-function-commas',
+    'babel-plugin-transform-async-to-generator',
+
+    // for React
+    'syntax-jsx',
+    'transform-react-jsx',
+
+    // some utilitis
+    'transform-inline-environment-variables',
+    'transform-node-env-inline',
+
+    // to remove duplicated helper methods inserted by babel.
+    'external-helpers',
+];
+
+if (isRelease) {
+    babelPlugins = babelPlugins.concat([
+        'transform-react-constant-elements',
+        'transform-react-inline-elements',
+    ]);
+}
+else {
+    babelPlugins = babelPlugins.concat([
+        'transform-react-jsx-source',
+    ]);
+}
+
+// https://github.com/rollup/rollup/wiki/JavaScript-API
+// https://github.com/rollup/rollup/wiki/Command-Line-Interface
+module.exports = {
+    entry: KAREN_ENTRY_POINT,
+    dest: path.resolve(KAREN_CLIENT_DIST_DIR, 'karen.js'),
+    format: 'cjs',
+    exports: 'none',
+    useStrict: true,
+    sourceMap: true,
+    treeshake: true,
+
+    plugins: [
+        // https://github.com/rollup/rollup-plugin-node-resolve
+        nodeResolve({
+            module: true,
+            main: true,
+            browser: true, // for browser
+            preferBuiltins: false, // linking for browser
+
+            // rollup does not have 'extensions' option,
+            // so we need to specify this option at here to import jsx file.
+            extensions: ['.js', '.jsx'],
+        }),
+
+        // https://github.com/rollup/rollup-plugin-commonjs
+        commonjs({
+            include: 'node_modules/**',
+            ignoreGlobal: true,
+            namedExports: {
+                'node_modules/option-t/src/index.js': ['Some', 'None', 'OptionBase'], // FIXME
+            },
+        }),
+
+        // https://github.com/rollup/rollup-plugin-babel
+        babel({
+            exclude: 'node_modules/**',
+            presets: babelPresets,
+            plugins: babelPlugins,
+        }),
+
+        // https://github.com/calvinmetcalf/rollup-plugin-node-builtins
+        nodeGlobals(),
+    ]
+};
diff --git a/tools/build/script.js b/tools/build/script.js
index 0a44f7d4..80aaba58 100644
--- a/tools/build/script.js
+++ b/tools/build/script.js
@@ -39,8 +39,19 @@ const { spawnChildProcess, assertReturnCode } = require('../spawn');
  *  @returns    {NodeJS.ReadableStream}
  */
 function runLinkerForClient(cwd, nodeModDir, entryPoint, distDir) {
-    const bin = path.resolve(nodeModDir, './.bin', getSuffixedCommandName('./webpack'));
-    const args = [];
+    let bin = '';
+    let args = [];
+    if (!!process.env.ENABLE_ROLLUP) {
+        bin = path.resolve(nodeModDir, './.bin', getSuffixedCommandName('./rollup'));
+        args = [
+            '-c',
+            path.resolve(cwd, 'rollup.config.js'),
+        ];
+    }
+    else {
+        bin = path.resolve(nodeModDir, './.bin', getSuffixedCommandName('./webpack'));
+    }
+
     const option = {
         cwd,
         stdio: 'inherit',