An extending portion of a vibration transmitting unit is capable of transmitting ultrasonic vibration from a proximal side to a distal side, and in the extending portion, a second component provided on the distal side with respect to a first component. A third component provided between the first component and the second component in the extending portion has a third cross-sectional area that is larger than a first cross-sectional area of the first component and is smaller than a second cross-sectional area of the second component, and one of vibration anti-nodes is positioned at the third component by the extending portion vibrating at a frequency in a predetermined frequency range.
