PURPOSE: To enable the high-accuracy positioning or a workpiece without damaging the workpiece and perform switching by the kinds of workpieces easily so as to improve reliability.

CONSTITUTION: Plural workpiece grip claws 11 movable forward/backward into an optional position from a workpiece grip position of gripping a workpiece on a workpiece positioning base 5 from the circumferential direction are disposed on the workpiece positioning base 5, and these workpiece grip claws 11 are synchronously driven to be opened/closed by actuators 9A, 10A through claw opening/closing mechanism. Accordingly, the workpiece 6 is not easily flawed, damaged, or the like, so that the stable positioning of the workpiece can be performed with high accuracy, and switching work by the kinds of workpieces can be also performed easily.