A treatment portion of a treatment device includes a pair of jaws, an energy emitter configured to emit energy to the living tissue of the treatment target, an insulating portion which is provided between the jaws and the energy emitter and which has electric insulation to cut off the flow of electricity from the energy emitter to the jaws, an outer edge which is provided in the jaw a flow path formed by the cooperation of the side of one of the jaws that is provided with the energy emitter facing the other jaw, the energy emitter, the insulating portion, and the outer edges, fluid emanating from the living tissue of the treatment target by the energy emitted from the energy emitter flowing into the flow path, and a support portion which is disposed in the flow path to cover at least a part of the flow path while maintaining an entrance to allow the fluid to flow into the flow path and which supports the living tissue to prevent the peripheral tissues of the living tissue of the treatment target from coming into the flow path.
