To provide a simple, durable and low-cost automatic folding storage lock device of a rear side wheel run-off prevention plate in a lifting device for a vehicle, ensuring the safety of the storage operation of the rear side wheel run-off prevention plate and eliminating the rocking and vibration thereof during traveling.

In the lifting device for the vehicle, the rear side wheel run-off prevention plate automatically standing/falling with respect to a ground-contact plate is installed at the rear end of a platform. Arm rods are provided on outer surfaces at both sides of the ground-contact plate. When the platform is stored/stood, a stiffening plate comprising a rear abutting part for turning the ground-contact plate and the rear side wheel run-off prevention plate related thereto by colliding the tip of the arm rod of the ground-contact plate and a lower abutting part for engaging the tip of the arm rod and locking it in that state is fixed to inner surfaces of right and left side frames. Restriction rods projectedly arranged on right and left outer side surfaces of the rear side wheel run-off prevention plate collides to pressing plates fixed to inner surfaces of the right and left side frames and the ground-contact plate and the rear side wheel detachment prevention plate are locked to a state of being folded/bent to a crest shape.