The medical treatment instrument of the present invention includes any one of a pair of opening and closing pieces, an opening and closing shaft portion that holds the pair of opening and closing pieces so as to be relatively rotatable, and a pair of opening and closing pieces so that the opening and closing shaft portion is a rotation center. A first gear fixed to one side, a second gear rotatable to transmit rotational force to the first gear, a diameter of the second gear fixed to the second gear coaxially with the second gear A rotating member having a larger diameter, and a power transmission member that is hung on the outer periphery of the rotating member and rotates the rotating member.本発明の医療用処置具は、一対の開閉片と、一対の開閉片を相対回動可能に保持する開閉軸部と、開閉軸部を回動中心とするように一対の開閉片のいずれか一方に固定された第一歯車と、第一歯車に対して回転力を伝達するために回転可能な第二歯車と、第二歯車と同軸をなして第二歯車に固定され第二歯車の直径よりも大きな直径を有する回転部材と、回転部材の外周に掛けられ回転部材を回転させる動力伝達部材とを備える。
