An ultrasonic transducer unit that generates ultrasonic vibration for treating living tissues has an ultrasonic transducer and a cover member that covers the ultrasonic transducer. A flexible sheath is coupled at one end to the cover member. A signal cable extends through the sheath and is connected at one end to the ultrasonic transducer. A transducer drive unit is connected to the other end of the signal cable. An operation unit is provided at the other end of the flexible sheath.