A vibration transmission member which is used together with a clamp portion and capable of transmitting vibration from an ultrasonic transducer extends from a proximal end portion toward a distal end portion, and the distal end portion is provided with a longitudinal portion extending from the proximal end portion to the distal end portion A ridge portion along the axis and located on a surface along the opening and closing direction in which the clamping portion moves by rotation is formed, and when vibration is input from the ultrasonic transducer, the ridge portion moves from the proximal end portion toward the distal end portion And the thickness along the opening and closing direction in which the clamp portion moves by rotation is smaller than the width of the tip portion in the width direction orthogonal to the opening and closing direction.クランプ部とともに使用され、超音波トランスデューサからの振動を伝達可能な振動伝達部材は、基端部から先端部に向かって延伸され、前記先端部には前記基端部から前記先端部にわたって延伸した長手軸に沿うとともに前記クランプ部が回動により移動する開閉方向に沿う面上に位置する稜部が形成され、前記超音波トランスデューサから振動が入力されることで前記基端部から前記先端部に向かって振動が伝達され、前記クランプ部が回動により移動する開閉方向に沿う厚さが、前記開閉方向に対して直交する幅方向の前記先端部の幅よりも小さい。
