Each of segments of a vibration transmitting member corresponds to a half-wave length portion between two mutually neighboring, corresponding vibration anti-nodes and is symmetric in the longitudinal direction with a vibration node between the vibration anti-nodes as a center. In each of recess segments included in the segments, the vibration node is located in a groove, and an intermediate extension extends from a proximal end to a distal end in the groove in a longitudinal direction. At least two of the recess segments are different from each other with respect to at least one of a dimension in the longitudinal direction of the intermediate extension and a cross-sectional area perpendicular to the longitudinal direction of the intermediate extension.
