An operation section structure of an treatment instrument for endoscopic use has: a hook knife inserted into a body cavity a wire 3 having a distal end connected to the hook knife a tubular flexible sheath 4 provided to an outer periphery of the wire 3 a current-canying plug 13 having a main unit having a distal end connected to the sheath 4 a sliding member 11 made of a conductive material and having a proximal end of the wire 3 fixed thereto, the sliding member 11 being capable of sliding on the main unit in longitudinal direction a operation member 12 capable of freely rotating in circumferential direction of the operation member 12 and attached to the sliding member 11 and a conductive section provided to the operation member 12, the conductive section being made of a conductive material providing conductivity by making contact with the sliding member 11. This configuration can rotate the distal end structure easily.
