PURPOSE: To dispense with complicated control of cutting for halving power by indenting a material to be cut off synchronously with a pair of cutters driven by a drive unit and having a converging section to cut off said material without shifting the pass line of said material.

CONSTITUTION: When a material 3 to be cut off reaches a predetermined position, a driving hydraulic cylinder 13 is activated to start the lift of an upper tool rest 7 and rotate a drive link through a second intermediate link 10. An upper tool rest 8 is lowered through a link 9. The material 3 is cut off by a single operation of a single drive source of the cylinder 13 without any shifts of the material from the pass line 18, with the upper and lower cutters 5, 6 being respectively synchronously lowered and lifted.