To eliminate the adjustment of backlash, improve working efficiency, and secure the sharpness of a cutter by forming gear for rotating a cutter into an overlap gear, pivotally moving a partial gear in the radial direction with a pin set to a fulcrum by a spring, and attaching an adjustment screw adjusting the position of the cutter in the radial direction.

An upper and a lower cutter 22, 23 of a cutting device are installed in respective grooves 20A, 21A of respective gears 20, 21 and fixed to a presser plate by respective bolts 31, 48. A partial overlap gear 37 which is arranged in a side of the lower gear 21 is pivotally moved in the radial direction with a pin 38 set to a fulcrum by a spring. This constitution can engage the upper gear 20 with the partial gear 37 at all times in a zero backlash state so that the upper and the lower cutters 22, 23 can hold an optimal clearance relation for a long time. The height of the upper cutter 23 is difficult to be adjust in the radial direction and the looseness of the bolt 31 easily causes distortion in the height dimension, however, the attachment of the adjustment screws 51, 53 to the upper and the lower cutters 22, 23 can solve these problems.