An endoscopic treatment instrument (1) is provided comprising: a cylinder (2) adapted to be fitted over a tip of an insertion section (I1) of an endoscope (E1)； a loop-shaped snare wire (SW) which protrudes in the cylinder from a snare sheath (SS) that is extendable and retractable with respect to the insertion section and which is extendable within the cylinder； a hooked portion (3) which is formed and radially inwardly extended from the circumference of the tip of cylinder and which holds the snare wire within the cylinder； a locking portion (5) which is provided on the hooked portion and retains a folded-back portion (W) of the snare wire that is forwardly moved toward the cylinder tip with respect to the snare sheath and by means of which the snare wire is turned upside-down around the folded-back portion.
