PURPOSE: To make it possible to detect a packing collapse at front and rear ends of subject matter of transfer securely and easily by once moving the subject matter to retreat to apply the rear end of a pallet to a second stopper.

CONSTITUTION: If detection of packing style is completed for both side parts and the front part, a cylinder unit 11 moves movable base 8A, 8B to retreat, and a conveyor 1 is driven to rotate reversely while a second stopper 5 is protruded. Subject matter of transfer 3 stopped by a first stopper 4 is moved to retreat until it is stopped with the rear end of a pallet 2 applied to the second stopper 5. If part or the whole of the subject matter 3 on the pallet 2 is protruding over the rear end of the pallet 2 at this time, at least one of photoelectric switches 25, 26 on the side of the second stopper 5 gets off, thereby occurrence of a packing collapse at the rear side of the subject matter 3 is detected.