An endoscopic-use treatment instrument includes: a wire an Y-shaped knife formed by a flexible material and is disposed at the distal end of the wire and used for treatment conducted in a body cavity a flexible sheath having the wire passing therethrough an operation section provided to the proximal end of the wire and capable of rotating the wire around an axial line a cylindrical bearing fixed to the distal end of the sheath a rotative member inserted into the bearing and capable of freely rotating relative to the bearing and a regulator section provided to the rotative member and regulating the rotation of the treatment member relative to the rotative member around the axial line. The rotation of the Y-shape knife relative to the rotative member around the axial line is regulated when the Y-shape knife makes contact with the regulator section.
