Provided is a vibrating section having an ultrasonic transducer of piezoelectric elements and a rear ultrasonic horn and a front ultrasonic horn, the horns being joined to the transducer. The ultrasonic transducer has a consumption power set at 8W or less. The ultrasonic horn has a flat front end surface, the area of the front end surface being set at 0.07 to 1 cm2.