Abstract: An automatic parking device for a multi-deck parking lot for motor vehicles is described. The device includes a carrier to carry a moveable platform from a parking position to a base or from a base to the parking position, and a hydraulic cylinder to move the moveable platform from the carrier to a fixed platform at an exit or from the fixed platform to the carrier. An inductor is provided on a moveable rod, which is driven by the hydraulic cylinder to move the moveable platform between the carrier and the platform and to automatically control an electromagnetic switch which drives two retaining iron strips to lock the moveable platform in the carrier.