To guarantee smooth entering work of a vehicle when the attitude must be corrected even if a correction angle is large.

When the vehicle 10 is shifted from a conveyor 27 to a conveyor 28, a control means changes the operating speeds of front conveyors 27a and 28a and rear conveyors 27b and 28b after receiving the detection signal of a second sensor 32. The vehicle 10 is applied with a first attitude correction before it is detected by a first sensor 31. Even if the entrance angle of the vehicle 10 onto the conveyor 27 of a berth 26 is large, the angle of the vehicle 10 is corrected to a small value when the vehicle 10 is detected by the first sensor 31, and a trouble is prevented that the vehicle 10 is detected by an extrusion sensor 30 before the attitude correction of the vehicle 10 is finished, thereby such a situation is eliminated that the operation of this mechanical parking device is temporarily stopped.