Provided is an endoscopic treatment instrument which is not prone to slip from the tissue of a lesion, and whereby a procedure can be safely performed. The present invention is provided with: a cylindrical member (10) having a distal end and a proximal end and having a lumen extending in the longitudinal direction； a linear object (20) which has a distal end and a proximal end, and which extends in the longitudinal direction and is disposed in the lumen of the cylindrical member (10)； and an electroconductive tip (30) which is provided on the distal-end side of the linear object (20) and is capable of projecting and retracting from the distal end (10d) of the cylindrical member (10)； the cylindrical member (10) having a point A and a point B which satisfy expression (1) further toward the distal-end side than the distal end (20d) of the linear object (20), on the outer surface of the cylindrical member (10) when the linear object (20) is moved furthest toward the distal-end side, in a cross section including the longitudinal axis of the cylindrical member (10). (1): Y/X >； 3 (In the expression, X is the absolute value of the difference in the positions of point A and point B in the axial direction of the cylindrical member 10, and Y is the absolute value of the difference in the positions of point A and point B in the radial direction of the cylindrical member 10.)L'invention concerne un instrument de traitement endoscopique qui n'est pas susceptible de glisser à partir du tissu d'une lésion, et par lequel une intervention peut être réalisée en toute sécurité. La présente invention comprend : un élément cylindrique (10) ayant une extrémité distale et une extrémité proximale et ayant une lumière s'étendant dans la direction longitudinale ； un objet linéaire (20) qui a une extrémité distale et une extrémité proximale, et qui s'étend dans la direction longitudinale et qui est disposé dans la lumière de l'élément cylindrique (10) ； et une pointe électroconductrice (30
