An endoscope treatment instrument includes: a sheath to be inserted into a channel of an endoscope a treatment portion at a distal end portion of the sheath an elongate member inserted into the sheath advancing and retracting, a distal end portion of the elongate member connected to the treatment portion, the elongate member advancing and retracting with respect to the sheath to operate the treatment portion and an operating portion on a proximal end portion of the sheath. The operating portion includes: an operating portion body connected to the sheath a slider movably along a direction of an axial line of the sheath with respect to the operating portion body and connected to a proximal end portion of the elongate member and a constant force spring portion biasing the slider towards a proximal end side with a constant force regardless of a position of the slider.
