PURPOSE: To ensure matching without causing any gap in both directions of opening/closing a door by forming a car door and a hoistway door panel in synchronous motion to always ensure connection of these at their edges.

CONSTITUTION: When a car door 4 begins to be displaced horizontally to the right with a given operating device, a roller 8 for the car door 4 begins to be moved along a special passage or a track belonging to a portion 9 fixed to a car. As a result of the motion of the roller 8, a deformable parallel quardrangle formed by a shape steel 3 opens its width and begins to be changed to the direction of contacting roller 6, 7 to push the rollers and turn a lock 1. Then, a corresponding switch 2 is opened and a hoistway door 5 is made open.