A forceps-type treatment instrument includes an end effector including a pair of clamps. In one of the clamps, a swinger is extended along an extending axis and swings relative to a supporting section around a swing axis extended along a direction intersecting with the extending axis and intersecting with an open and close direction of the clamp. A regulating section regulates movement of the swinger in the direction along the swing axis in at least two portions separated from each other in a direction along the extending axis, and thereby prevents rotation of the swinger around a rotation axis along the open and close direction.
