PURPOSE: To provide a device of simple structure and easy adjustment, by making the device of a porjecting member located at a hinge and of a stop located on chassis.

CONSTITUTION: The projecting member 9 is provided at the rear edge of a hinge bracket 6. The stop 10 is secured to the side of rear part of a frame 2 so that the stop 10 comes into contact with the projecting member 9 when the bed is tilted most. The tilt of the bed 5 is performed by the expansion and contraction of piston rod 12 combined with a hydraulic cylinder 11 installed between the bed 5 and the chassis 1. The bed 5 is smoothly tilted by the small output of the hydraulic cylinder. Therefore, the structre is simple and the manufacturing and adjustment are easy