A grasping treatment instrument includes a grasping piece, and a supporting member opening and closing relative to the grasping piece. A clamp member is provided between the supporting member and the grasping piece in open and close directions of the supporting member, and the clamp member includes an opposed surface opposed to the grasping piece, and a back surface facing to an opposite side of the opposed surface. The grasping treatment instrument includes a cover member made of a material having lower thermal conductivity than the clamp member, and the cover member covers the clamp member from the back surface side in a part on a distal side with respect to a position where the clamp member is pivotally supported.