PURPOSE: To prevent side deflecting and breaking of a cutting edge even without high accurately cutting a mounting hole of the cutting edge.

CONSTITUTION: A cutter comprises the first/second ceramic piezoelectric transducers 17, 19 generating ultrasonic vibration, horn 2 transmitting the ultrasonic vibration from the first/second ceramic piezoelectric transducers 17, 19 output, case 11 storing the first/second ceramic piezoelectric transducers 17, 19 and the horn 2 and a cutting edge 1 provided protrudably from a point end of the case 11. A cutting edge mounting hole 3, having a cutting edge mounting surface 3a, is formed in a point end part of the horn 2, and a screw mounting hole 4 is formed to be inserted through the cutting edge mounting hole 3 from a peripheral part of the horn 2 further to be opposed to the cutting edge mounting surface 3a, to fix the cutting edge 1 to the cutting edge mounting hole 3 by a rolled thin plate material 6, inserted to be interposed between the cutting edge 1 and the cutting edge mounting surface 3a to have a surface smoother than the cutting edge mounting surface 3a, and by a set screw 5 screwed to the screw mounting hole 4.