A probe treating a living tissue in cooperation with a jaw pivoting on a supporting point includes a treatment portion including a proximal end to which ultrasonic vibration generated from an ultrasonic transducer unit is transmitted； a distal end to which the ultrasonic vibration is transmitted from the proximal end； a holding surface holding the living tissue between the holding surface and the jaw； a back surface serving as a rear surface of the holding surface； a side surface extending from the proximal end to the distal end and being different from the holding surface； and a stress release portion provided between the distal end and the proximal end and on the side surface and releasing stress to stop development of a crack when the crack is produced in the holding surface or the back surface by external forces applied during the treatment of the living tissue.
