PURPOSE: To hold a pallet in a stable manner by installing an engagement device oppositely to the most rising position of the front/rear end parts of the pallet and carrying out holding and release by projecting and retreating an engagement piece to the raising and lowering region at the front and rear end parts of the pallet.

CONSTITUTION: When a parked vehicle in the most left row on the uppermost stage in four rows three stages in delivered, the vacant place in the most right row on the lowermost stage is utilized, and all the pallets on the lowermost stage are transferred to the contiguous row along rails 6 and 6'. After the vacant place in the most right row is formed, all the bases of the unit in the next stage are transferred to the right contiguous row along rails 5 and 5', and each vacant place is formed on the next stage in the most left row and the lowest stage. Then, the parked vehicle in the left row on the uppermost stage is lowered and delivered. In this case, in order to hold the pallet group which can be raised and lowered at each most rising position, an engagement piece 37 is projected and retreated as engagement device to the rising/ lowing at the front/rear end parts of each pallet. A power cylinder 31 for driving the engagement piece 37 is installed at the most rising position at the front and rear end parts of the pallet.