PURPOSE: To apply no large load to a bed portion erecting and laying mechanism and not to damage any obstacle by providing a detecting member for detecting separation of a bed portion erecting and laying mechanism from a bed portion, on the bed erecting and laying mechanism, and stopping the erecting and laying mechanism in the case of detecting its separation from the bed portion.

CONSTITUTION: A bed portion erecting and laying mechanism 4 is disposed between a bed frame and a back bed 3, and a displacing member 11 as a detecting member is attached to an operating link 8 brought into contact with the back bed 3 through a roller 7. And an emergency stop switch 12 is provided on the member 11. If there is an obstacle between the back bed 3 and the bed frame 2, the back bed 3 is checked from being lowered. As the bed portion erecting and laying mechanism 4 is in the state of operation, the operating link 8 continues to turn counter-clockwise together with the displacing member 11, so that the link and the member are separated from the roller 7 of the back bed 3 and the displacing member 11 is displaced along a sliding hole 14 bored obliquely upward in such a manner as to point the back bed 3 by the resilient force of the spring member 17. At this time, the displacing member 11 is a little moved horizontally, and an operating element 12a of the emergency stop switch 12 is pressed by a part 13 thereof to operate.