To reduce burrs and noise by providing an oscillator having a punch which is vertically oscillated through high-speed rotation of a disk and a clamp of a work, and demarcating an oscillation part by an oscillation chamber filled with oil between the oscillator and the disk.

A rack shaft stock 11 in which a core is inserted is clamped by a clamp 25, a lock member 71 is interposed between a lower frame 21A and a base 22, and the rack shaft stock is placed at the work starting position. An oscillator 26 is vertically oscillated at high speed by an oscillation device 27, a rack toothed surface of a punch 20 is pressed against the rack shaft stock 11, the rack shaft stock 11 is gradually moved upward by a bellows cylinder 61 to form the rack tooth. Punch-forming is completed when the upper end of a lower frame 23 is abutted on the lower end of an upper frame 24, the lock member 71 is withdrawn to take out a product. Because an oscillation part 27A is demarcated by an oscillation chamber 47 filled with oil, the mechanical resistance is reduced by the oil lubrication, and the striking noise and vibration can be reduced by the damping effect of oil, and generation of burrs can be reduced.