Respective divided segments of a collet are moved radially outward by moving an arbor axially. The respective divided segments thereby press an inner circumferential surface of a stator core of a stator from radially inside such that the stator is held coaxially by the collet. Next, shaping rollers are lowered so as to press an outer circumferential surface of the stator core. The stator is rotated by rotating the collet in that state. Thus, the inner circumferential surface of the stator core is compressed and plastically deformed so as to conform to the collet and the outer circumferential surface of the stator core is compressed and plastically deformed by the shaping rollers, correcting the inner circumferential surface and the outer circumferential surface of the stator core so as to be coaxial and so as to have a high degree of roundness.