Problems to be SolvedSurgical operation or others excellent in operability, safety, operation efficiency and precision are realized by outputting a vertical-torsional composite vibration through conversion processing of the longitudinal vibration from an ultrasonic oscillation mechanism and reducing the displacement speed of the non-working plane in a female portion less than the speed of the working plane.Means to Solve the ProblemA configuration, comprising an ultrasonic oscillation mechanism composed of a longitudinal vibration element, a backing plate and a front plate for generating an ultrasonic vibration, a horn coupled with the ultrasonic oscillation mechanism for amplifying the vibration transmitted from said ultrasonic oscillation mechanism, a vibration conversion mechanism for converting the vibration transmitted from said ultrasonic oscillation mechanism into a composite vibration composed of a longitudinal vibration in the horn central axial direction and a torsional vibration having the horn central axis as fulcrum, and a female portion provided with a working plane and disposed at said horn tip, wherein said ultrasonic oscillation mechanism is composed of one or more groove portions formed on the circumferential surface of the horn or said backing plate, and a speed variation mechanism of torsional vibration in said composite vibration is formed in the female portion, in order to reduce the reciprocating rotation speed of the non-working plane less than the speed of the working plane.