A treatment device used together with an endoscope, has a guide pipe and a movement mechanism. The guide pipe has a first pipe having a curving portion and a second pipe continuous with a proximal side of the curving portion. The curving portion has, in its inner circumferential surface, a bent surface bent to the second pipe, and bending the flow direction of the fluid discharged from the distal end of the sheath in a state where the distal end of the sheath is located near the distal end of the second pipe. The movement mechanism protrudes a distal surface of the insertion portion from the distal end of the sheath and brings the distal surface closer to or into abutment with the bent surface in a state where the distal end of the sheath is disposed near the distal end of the second pipe.
