With respect to a forceps type (scissors type) treatment instrument 7 including an ultrasound probe 52 that protrudes from a treatment instrument main body 20 at a position separated to a distal end side from a shaft portion 22 that pivotally supports a clamp arm 21 swingably with respect to the treatment instrument main body 20, and a jaw 61 that is provided at the clamp arm 21 in a position separated to a distal end side from the shaft portion 22, and is displaceable between a closed state contacting the ultrasound probe 52 and an opened state separated from the ultrasound probe 52 by being linked with swing action of the clamp arm 21, stoppers 70 are extendedly provided toward a clamp arm 21 side from a treatment instrument main body 20 side in a state in which edge portions at a distal end side are set to be located at a distal end side from a locus of a proximal end of the jaw 61 following displacement of a base 60, and by the stoppers 70, entry of a living body into a gap (inside of a treatment incapable region 64) of the treatment instrument main body 20 and the clamp arm 21 between a proximal end portion of the jaw 61 and the shaft portion 22 is restricted, when the jaw 61 is in the opened state.
