npm install sass-loader node-sass --save-dev

exports.cssLoaders = function (options) {
 options = options || {}

 var cssLoader = {
 loader: 'css-loader',
 options: {
 minimize: process.env.NODE_ENV === 'production',
 sourceMap: options.sourceMap
 }
 }

 // generate loader string to be used with extract text plugin
 function generateLoaders (loader, loaderOptions) {
 var loaders = [cssLoader]
 if (loader) {
 loaders.push({
 loader: loader + '-loader',
 options: Object.assign({}, loaderOptions, {
 sourceMap: options.sourceMap
 })
 })
 }

 // Extract CSS when that option is specified
 // (which is the case during production build)
 if (options.extract) {
 return ExtractTextPlugin.extract({
 use: loaders,
 fallback: 'vue-style-loader'
 })
 } else {
 return ['vue-style-loader'].concat(loaders)
 }
 }

 // https://vue-loader.vuejs.org/en/configurations/extract-css.html
 return {
 css: generateLoaders(),
 postcss: generateLoaders(),
 less: generateLoaders('less'),
 sass: generateLoaders('sass', { indentedSyntax: true }),
 scss: generateLoaders('sass'),
 stylus: generateLoaders('stylus'),
 styl: generateLoaders('stylus')
 }
}

<style scoped lang="sass">
 xxxx
 xxxx
</style>