An ultrasonic transducer includes driving source attached to an outer periphery of a bolt with being sandwiched between a distal side block and a proximal side block in a direction along a longitudinal axis, and the driving source includes a piezoelectric element generating ultrasonic vibration by an electric energy being supplied. By transmission of the ultrasonic vibration generated in the piezoelectric element, the ultrasonic transducer in a state in which a first vibration node that is generated in the driving source and a second vibration node that is generated in the bolt are prevented from being displaced with respect to each other in the direction along the longitudinal axis
