WooCommerce - Custom CSS

functions.php

<?php

function my_theme_woocommerce_enqueue_styles( $styles ) {
	$base_url = str_replace( array( 'http:', 'https:' ), '', get_stylesheet_directory_uri() ) . '/inc/woocommerce/css/';

	$styles['woocommerce-layout']['src']      = $base_url . 'woocommerce-layout.css';
	$styles['woocommerce-smallscreen']['src'] = $base_url . 'woocommerce-smallscreen.css';
	$styles['woocommerce-general']['src']     = $base_url . 'woocommerce.css';

	return $styles;
}

add_filter( 'woocommerce_enqueue_styles', 'my_theme_woocommerce_enqueue_styles' );