To obtain a beautiful cut plane with no deformed cut section by using a torsion cutting method in cutting a cylindrical or polygonal object.

A cutting tool consists of an upper shearing portion 1 and a lower shearing portion 2, both shearing portions 1, 2 being provided with cutting blades 6 contacting each other. These cutting blades 6 are provided as closest as possible to the vertical plane 7 of a plate 3 to be cut which has a depression 10 to insert a skeleton forming screw, e.g. in a sectionally rectangular shape therein. Both shearing portions 1, 2 are turned by 15 degrees or more around the vertical axis 4 of the plate 3 to be cut, almost perpendicular to rotational planes 8 of the shearing portions 1, 2, for cutting the plate 3 in a torsional condition.