An ultrasound transducer includes: a drive unit including a piezoelectric device； a proximal end block； and a distal end block. The distal end block includes a first portion, a supported portion, a second portion, and a third portion. The distal end block is configured such that a position of a boundary between the second portion and the third portion corresponds to or substantially corresponds to an antinode of the ultrasonic vibration while the piezoelectric device generates the ultrasonic vibration, and the ultrasonic vibration is being propagated to the proximal end block, the first portion, the second portion, and the third portion. A resonance frequency of the ultrasonic vibration differs according to a position of the boundary between the second portion and the third portion under a condition that a distance from the supported portion to a distal end of the third portion along the longitudinal axis is constant.
