For the purpose of more reliably capturing and removing even a gallstone that has gotten into a stepped portion formed in a lopsided manner at a boundary between the bile duct and the duodenal papilla, an endoscope treatment tool according to the present invention includes: a sheath having a lumen (2a) that extends along a longitudinal axis thereof； a basket portion (4) that is configured to protrude from the lumen (2a) and that is formed of at least one elastic wire (4a)； and a manipulation wire (5) that causes the basket portion (4) to be moved forward and backward, wherein the elastic wire (4a) has a maximum-outer-diameter portion (P1) between a distal end and a proximal end of the elastic wire (4a) and a largest portion (P2) that, between the maximum-outer-diameter portion (P2) and the proximal end of the elastic wire (4a), reaches the maximum size in an opposite direction from maximum-outer-diameter portion (P1) in a side view from a direction that is orthogonal to a perpendicular line (Lv) drawn to a center axis (O) from the maximum-outer-diameter portion (P1), and wherein, in a front view of the basket portion (4), the largest portion (P2) is positioned on an opposite side from the side of the maximum-outer-diameter portion (P1) with respect to a straight line that is orthogonal to the perpendicular line (Lv) on the center axis (O).
