@Kenta: If you just want to make small changes, then you can add your responsive style in “Appearance => Theme Options => Custom CSS” box. But if you want to totally change responsive.css then you need to dequeue parent style and add you child file.
So, if you want to edit it from your child theme then first, you need to create responsive.css and functions.php file in your child theme. If you download sample child theme from http://catchthemes.com/blog/create-child-theme-wordpress/, then you will get this. You just need to add responsive.css file.
Then, you need to add the following code in your functions.php file in your child theme
// Remove Parent theme responsive.css and adding new responsive.css in child theme
function adventurous_child_enqueue_scripts() {
wp_dequeue_style( 'adventurous-responsive' );
wp_enqueue_style( 'adventurous-child-responsive', get_stylesheet_directory_uri() . '/responsive.css' );
}
add_action( 'wp_enqueue_scripts', 'adventurous_child_enqueue_scripts', 11 );
.
