PROBLEM TO BE SOLVED: To achieve long life of a probe and a jaw by preventing unnecessary long-time treatment.SOLUTION: An ultrasonic treatment instrument includes: a clamp arm journaled to a sheath in which an ultrasonic probe is inserted to freely oscillate through a shaft section； a base having a first tip part and a first base end part and provided on the clamp arm on the tip side from the shaft section； a jaw having a second tip part and a second base end part, supported on the base to oscillate around the axis extending in the width direction vertical to a longitudinal axis, and forming the space between the second base end part and the pedestal by locating the second tip part on the tip side from the first tip part and locating the second base end part on the base end side from the first tip part； an operation part for operating the opening and closing direction of the jaw； and a stopper extending from the sheath in the opening and closing direction, formed to cover the space between the second base end part and the base, and located on the tip side from the locus drawn by the second end part when the operation part is operated from the closing state to the opening state.【課題】処置時間の不要な長大化を防止し、プローブやジョー等の長寿命化を実現する。【解決手段】超音波プローブが挿通するシースに軸部を介して揺動自在に軸支されたクランプアームと、第１の先端部と第１の基端部とを有し、クランプアームに前記軸部よりも先端側に設けられた台座と、第２の先端部と第２の基端部とを有し長手軸に垂直な幅方向に延在する軸周りに揺動可能に台座に対して支持され、第２の先端部が第１の先端部より先端側に位置し、第２の基端部が第１の先端部よりも基端側に位置して第２の基端部と台座との空間を形成するジョーと、ジョーの開閉方向に操作する操作部と、シースから開閉方向について延出し、第２の基端部と台座との空間を覆うように形成され、操作部を閉状態から開状態に操作する際に第２の基端部が描く軌跡よりも先端側に位置するストッパとを備える。【選択図】図１
