PURPOSE: To disperse the pushing pressure applied to a card material and perform high accurate cutting by rotating a cutter arranged perpendicularly around the axis thereof and lowering it making it slant at specified angles to a plastic card base material.

CONSTITUTION: A cutter 12 rotating in relation to a card base material 10 is made to abut to a point A and is rotated anticlockwise to a point B in the card base material on a plane and lowered being inclined in relation to the cross section thereof. In the next step, the cutter 12 is lowered to a point C located more deeply than the point B and moreover to a point D located on the bottom face of a recess section 11 being inclined at a specified angle. The cutter 12 is made to move in a horizontal direction to cut the card base material 10 for forming the recess section 11, and then, extracted diagonally and upward. As a result, the pushing pressure applied to the card base material 10 from the cutter 12 can be dispersed, which can prevent the settling caused by the pressure concentration in the card base material 10.