An automatic pallet changer 2 includes: a pallet housing unit 11 having a plurality of pallet placement portions; and a pallet transfer unit 12 configured to transfer a pallet P that is at a required pallet placement portion and has an un-machined workpiece W attached thereto to a standby station S2 and configured to transfer a pallet P that is at the standby station S2 and has a machined workpiece W attached thereto to a required pallet placement portion. The pallet housing unit 11 includes: main housing portions 13a to 13f that have a plurality of rows of pallet placement portions, each having a plurality of stages, and are disposed to face the machine tool body 1; and three rows of secondary housing portions 14 that have one stage of pallet placement portions and are disposed above the machine tool body 1.