A horn 32b, a piezoelectric element 32d, and a base 32f, of an ultrasonic transducer 32 are formed to have a substantial semi-cylindrical shape having a side plane 32g, and a link body part 34c used to open and close a gripper 34 is provided. Consequently, a part to be treated inside a patient body can be grasped between a distal end treatment part 32a and a grasp member of a grasp part 34, and the link body part 34c can be effectively housed inside a sheath.
