A surgical instrument comprises: an insertion unit a treatment unit provided at one end of the insertion unit, capable of turning about one axis, and comprising a clamping section capable of opening and closing action an operation unit provided at the other end of the insertion unit a turn force transmission mechanism, provided between the operation unit and the treatment unit along the insertion unit, and transmitting from the operation unit to the treatment unit a turn force to turn the treatment unit an opening and closing force transmission mechanism, provided between the operation unit and the treatment unit along the insertion unit, and transmitting from the operation unit to the treatment unit an opening and closing force to open and close the clamping section and a common operation mechanism provided in the operation unit for applying the turn force to the turn force transmission mechanism and applying the opening and closing force to the opening and closing transmission mechanism.
