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 as at least one of the pair of pinching surfaces a cutting member 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 and a plurality of gap maintaining portions provided at a fixed interval along an axial direction at an end face of the guiding groove in such a manner that the end face on the guiding groove side and an inner face on the energy output section side are flush with each other.
