To perform sure clamping for a crank pin when it is machined and accurate machining.

Workpiece receiving bases 36 for mounting and supporting the journals J1 and J2 of a crankshaft are provided. A clamp roller 63 for clamping the journals J1 and J2 mounted and supported by the workpiece receiving bases 36 therebetween is provided. The workpiece receiving bases 36 and the clamp roller 63 are integrally rotated around positions shifted from the axial centers of the journals J1 and J2. The clamp roller 63 clamps the journals J1 and J2 in two spots separated in the circumferential directions thereof.