PURPOSE: To open and close a door only by means of supports by erecting each one support on both ends of a closed door frontage and disposing rope to a support arm by a lock mechanism, and engaging the a guide rail in the longitudinal direction of the inside surface thereof and each one floating rod having an engaging and disengaging portion diposed on the lower end a little to the top of the inside surface.

CONSTITUTION: A guide rail 32a is disposed along the longitudinal direction of the inside surface of each one support 31, 32 erected on both ends of a closed door frontage. Further, a floating rod 52 is disposed on the inside surface a little to the top of each support 31, 32, and an engaging and disengaging portion 52b is disposed on the lower end of the floating rod 52. When the door 1 is opened, an upper projection 12a engages with the engaging and disengaging portion 52b of the floating rod 52, and only the upper projection 12a is forced to reach a position for separating from the guide rail 32a. The floating rod 52 and the door 1 are bent at the engaging and disengaging portion 52b to be substantially horizontal and be in the door open limit. Thus, one erected rail 32a is enough one side each.