In order to more reliably hook and evacuate gallstones that have penetrated into a stepped portion formed toward a boundary between the bile duct and the duodenal papilla, this treatment tool (1) for an endoscope comprises: a sheath (2) having a lumen which extends along a longitudinal axis； a basket (4) that protrudes from the lumen and that has one or more elastic wires (4a)； and an operation wire (5) that advances/retracts the basket in the lengthwise direction of the sheath. The elastic wire includes: a maximum outer diameter part in which the outer diameter of the basket reaches a maximum between the distal end and the base end of the elastic wire； a first maximal part that becomes maximized in the opposite direction of the maximum outer diameter part relative to the center axis of the basket between the maximum outer diameter part and the base end of the elastic wire in a side view from the direction orthogonal to a perpendicular line from the maximum outer diameter part to the center axis； and a second maximal part that becomes maximized at a position spaced apart from the perpendicular line between the maximum outer diameter part and the first maximal part. The first maximal part is positioned on the opposite side of the maximum outer diameter part side relative to a straight line that is orthogonal to the perpendicular line on the center axis in a front view of the basket.Afin d'accrocher et d'évacuer de manière plus fiable des calculs biliaires qui ont pénétré dans une partie étagée formée vers une frontière entre le canal biliaire et la papille duodénale, l'invention décrit un instrument de traitement (1) pour un endoscope comprenant : une gaine (2) ayant une lumière qui s'étend le long d'un axe longitudinal ； un panier (4) qui fait saillie à partir de la lumière et qui a un ou plusieurs fils élastiques (4a) ； et un fil d'actionnement (5) qui fait avancer/rétracter le panier dans le sens de la longueur de la gaine. Le fil élastique comprend : une partie d
