Locking device for the opening of a door including two opposite members apt to be mounted to a door and to a post, respectively, and provided with housing holes of screws for the engagement with a surface, one of the bodies including a solid body except for a cavity provided on one of the side walls, the other one of the bodies including an outside shell internally provided with a housing cavity of a sliding body, characterised in that a lock block for the movement of the sliding body is furthermore provided, housed within a cavity provided on the top surface of the outer shell as well as dampening and thrust structure of the sliding body.