PURPOSE: To stop a door at an optional opening position by a method in which an input shaft to be turned toward closing direction by a part is braked by a braker, and a stopper is coupled with a coupler.

CONSTITUTION: When a door is opened, an input shaft 3 is turned to end support to a part 8, and the shaft 3 is reversely turned by the part 8 to turn the door to closing direction. In this case, the rotation of the shaft 3 is transmitted to a brake 13 through a speed-increasing wheel train 11 to brake the closing action of the door. When the stopper is on the coupling position, it is coupled with the coupler of the train 11 to stop the turning of the door. The coupling position of the stopper is held by a change spring 19. When the door is forcibly turned toward closing direction and the stopper is pushed, the position is held by the change spring 19 to release the coupling action to allow the door to close.