A workpiece holder, which does not require actual parts matching as required in a related-art automatic pallet changer, and has higher maintainability than a related-art automatic pallet changer. The workpiece-side jig includes a workpiece-side fitting element provided on a surface opposed to the master-side jig. The master-side jig includes: a master-side fitting element to be fitted to the workpiece-side fitting element, which is provided on a surface opposed to the workpiece-side jig; a rotary pressing member to be brought into abutment against the workpiece-side fitting element fitted to the master-side fitting element to press the workpiece-side fitting element toward the master-side jig; and a rotational drive source configured to rotate the rotary pressing member. When the rotary pressing member is rotated by the rotational drive source, the rotary pressing member is brought into abutment against the workpiece-side fitting element to press the workpiece-side fitting element toward the master-side jig.