A medical-treatment-tool according to the present invention is provided with: a inserting-portion； a gripping-piece pivots about a shaft orthogonal to a longitudinal axis of the inserting-portion； a driving-portion generates a motive power with which the gripping-piece is driven； a first motive-power transmitting member transmits the motive power to the inserting-portion； a motive-power amplifying mechanism amplifies the motive power； a pulley secured to the shaft of the gripping-piece； a wire-like second motive-power transmitting member wound around the pulley, transmits amplified the motive power to the pulley, and rotates the pulley about the shaft, thus causing the gripping-piece to be pivoted. The motive-power amplifying mechanism is a movable-pulley supported to move in a direction along the longitudinal axis of the inserting-portion, the first motive-power transmitting member is a wire-like member wound around the movable-pulley, and end of the second motive-power transmitting member is attached to the rotation shaft of the movable-pulley.
