The operation member attached to the housing of the medical treatment instrument has an operation surface exposed to the outside of the housing and pressed by operation input. A step forming portion is provided in the vicinity of the operation surface on the exposed surface of the housing, and the step forming portion is in a state in which the portion closer to the operating surface is lower than the portion far from the operating surface , A step is formed in the width direction of the housing. The step lowers at least a part of the outer edge of the operation surface as compared with the portion of the step distant from the operation surface.医療処置具のハウジングに取付けられる操作部材は、前記ハウジングの外部に対して露出し、操作入力によって押圧される操作面を備える。前記ハウジングの露出表面において前記操作面の近傍には、段差形成部が設けられ、前記段差形成部は、前記操作面に近い側の部位が前記操作面から遠い側の部位に比べて低くなる状態に、前記ハウジングの幅方向について段差を形成する。前記段差は、前記操作面の外縁の少なくとも一部を、前記段差の前記操作面から遠い側の前記部位に比べて低くする。
