This treatment instrument for an endoscope is provided with: a sheath； and a balloon provided at the distal end of the sheath, the balloon being configured so as to be capable of being expanded by fluid supplied thereto, from a folded initial shape into an unfolded expanded shape, the balloon having a first region and a second region, the first region and the second region being provided at the longitudinally opposite ends of the balloon, the balloon further having an intermediate section provided between the first region and the second region. The treatment instrument for an endoscope is configured so that: in the initial state of the balloon, the amount of residual strain in the intermediate section will be greater than that in the first region and that in the second region； when pressure in the balloon has a first inner pressure value, the first region and the second region will be unfolded faster than the intermediate section, thereby causing the first region and the second region to have a greater diameter than the intermediate section； and when pressure in the balloon has a second inner pressure value greater than the first inner pressure value, the first region, the second region, and the intermediate section will be unfolded into the expanded shape, thereby causing the intermediate section and both the first region and the second region to have substantially the same diameter.La présente invention concerne un instrument de traitement destiné à un endoscope comprenant : une gaine ； et un ballonnet disposé au niveau de l'extrémité distale de la gaine, le ballonnet étant conçu de sorte à pouvoir être dilaté par son alimentation en fluide, d'une forme initiale pliée en une forme dilatée dépliée, le ballonnet comprenant une première région et une seconde région, la première région et la seconde région étant disposées à des extrémités longitudinalement opposées du ballonnet, le ballonnet comprenant en outre une section intermédiaire disposée entre la première régi
