Provided is a medical treatment instrument including: a pair of openable/closable pinching portions that pinch a body tissue via a pair of pinching surfaces facing each other an energy output section provided in at least one of the pair of pinching portions, the energy output section including an energy application surface for applying energy to the body tissue as at least one of the pair of pinching surfaces a cutting member for cutting the body tissue that is capable of advancing/retracting inside the pinching portion a guiding groove including a recess portion in the energy application surface, the guiding groove guiding the cutting member in such a manner that the cutting member can advance/retract inside the pinching portions and gap maintaining portions arranged so as to be adjacent to a surface that is flush with an inner face of the recess portion of the guiding groove or be embedded in the guiding groove, the gap maintaining portions projecting between the pair of pinching surfaces facing each other when the pair of pinching portions are closed, to thereby maintain a fixed distance between the pair of pinching surfaces.
