PURPOSE: To obtain a flat cutting face at all times by pressing a movable cutting edge toward a normal direction after slightly pressing said edge toward a direction different from a cutting direction when a rod material is inserted in the holes of fixed and movable cutting edges and cut with the shift of the movable cutting edge.

CONSTITUTION: After a rod material 3 has been inserted in the through-holes 1a and 2a of a fixed cutting edge 1 and a movable cutting edge 2 for contact with a stopper 4, a piston rod 15a is contracted, a spacer 16 is drawn out and another piston rod 11 is pushed up, thereby pressing the movable cutting edge 2 upward. According to the aforesaid constitution, a shear force works between the fixed cutting edge 1 and the movable cutting edge 2 and a lead crack is generated on the rod material 3. Then, a ram 5 is lowered for hammering the movable cutting edge 2 and cutting the rod material 3. In this case, a crack due to pressing by the ram 5 propagates toward the lead crack as already existing. Therefore, the final shear force is small and a cutting face is clean, thereby improving cutting accuracy.