PURPOSE: To enable the cutting of a columnar metal or a pipe to a smooth edge by applying a constitution wherein a movable cutter inserted with a columnar workpiece having the same inner hole as a fixed cutter coaxially arranged is moved eccentrically for circumferential cutting all at once.

CONSTITUTION: When a drive cylinder 8 is turned by a driving gear 12 in a cutting process, the external surface thereof gives circular motion along the circumference of the inner large bore part of a base 1 about a central point o' as an axial center via an outer bearing 10. And the internal surface of said cylinder 8 has a central point at an eccentric point o and gives eccentric motion due to a different axial center, when the drive cylinder 8 is rotated along the circumference of the inner large bore part of the base 1 via the bearing 10. The central point o turns 360° about the central point o' with the rotation of the drive cylinder 8 and returns to the original position. Therefore, the central point o of a movable cutter 5 is shifted to o', and the maximum portion a of the wall thickness of the drive cylinder 8 and the minimum portion b thereof are exchanged for each other in position after 180° rotation. Concurrently therewith, the movable cutter 5 gives circular motion without rotation about a fixed cutter 4 and shearing takes place smoothly at one edge where said cutters are in contact with each other.