Disclosed is a two way swinging door opening gap control device for controlling the movements of companion animals that is detachably attached to the existing door and door frame with ease, without any structural change or damage, thereby being applied conveniently to various types of doors, and that controls an opening gap of the door to allow the companion animals to freely enter through the door, to prevent the door from being excessively opened by external wind or animals entering therethrough, and to limit the spaces the animals can enter according to animal sizes to thus provide individual living spaces for the animals. According to the present invention, the opening gap control device largely includes a gap control band 100, a locking pin module 200, and a locking holder module 300.