A front mass of a vibration generating unit included a flange portion supported, and a block portion provided on a proximal side with respect to the flange portion. A distal end of the element unit abuts on a proximal end of the block portion. Ultrasonic vibration generated in a piezoelectric element is transmitted, thereby vibrating the front mass in a predetermined frequency region where a referential vibration anti-node, which is one of vibration anti-nodes located on the proximal side with respect to the flange portion, is located at a boundary position between the block portion and the element unit or in the vicinity of the boundary position.
