PURPOSE: To keep the mechanical accuracy of a shear-off machine constant and enhance the rate of operation of a process line, by using a hydraulic cylinder to swing the shear-off machine to perform shearing-off at a prescribed swing angle.

CONSTITUTION: When a cut-off instruction is applied, a connecting rod 8 is pushed down so that an upper cutter holder 5 is moved down and a balancing cylinder 7 is pushed down. Oil in the cylinder 7 flows to an accumulator 13 and the head of a swinging cylinder 9. Because the upper cutter holder 5 is moved down, the rod of the cylinder 9 is protruded to swing a housing not shown in the drawing. The upper cutter holder 5 and a lower cutter holder not shown in the drawing are overlapped with each other to shear off a material. At that time, the material is sheared off at a prescribed swing angle even if the moving speed of the material changes.