An endoscope treatment tool comprising: a flexible sheath; a manipulation wire inserted through the flexible sheath so as to freely advance and retract; and a basket portion which is connected to a distal side of the manipulation wire, is constituted by a locking portion provided at a distal end of the basket portion, and a plurality of elastic wires integrated by the locking portion, and opens and closes in a radial direction orthogonal to a central axis of the manipulation wire, wherein a maximum outside diameter portion of the basket portion is at a position closer to the locking portion than a midpoint between a proximal end of the basket portion and the locking portion in a direction of the central axis, and wherein the plurality of elastic wires is formed in a shape of a helix characterized in that, each of the plurality of elastic wires is wound in a same direction over an entire length of the plurality of elastic wires, a winding pitch of the plurality of elastic wires becomes gradually smaller in a direction from a proximal side of the manipulation wire to the distal side of the manipulation wire, a gap between the plurality of the elastic wires is smaller at a portion between the distal end of the manipulation wire and the maximum outside diameter portion than at a portion between the proximal end side of the manipulation wire and the maximum outside diameter portion, and a tangential line of each of the plurality of elastic wires in the maximum outside diameter portion is inclined at an angle of 45° or less with respect to a plane orthogonal to the central axis without an external force applied to the basket portion, and thereby, when a proximal side of the basket portion is reduced, the maximum outside diameter portion is pushed outward in the radial direction by a first amount which is substantially a same as a second amount by which the proximal side of the basket portion is reduced inward in the radial direction such that an outside diameter of the maximum outside diameter portion is maintained at substantially a same size as the outside diameter before the proximal side of the basket portion is reduced. a flexible sheath; a manipulation wire inserted through the flexible sheath so as to freely advance and retract; and a basket portion which is connected to a distal side of the manipulation wire, is constituted by a locking portion provided at a distal end of the basket portion, and a plurality of elastic wires integrated by the locking portion, and opens and closes in a radial direction orthogonal to a central axis of the manipulation wire, wherein a maximum outside diameter portion of the basket portion is at a position closer to the locking portion than a midpoint between a proximal end of the basket portion and the locking portion in a direction of the central axis, and wherein the plurality of elastic wires is formed in a shape of a helix characterized in that, each of the plurality of elastic wires is wound in a same direction over an entire length of the plurality of elastic wires, a winding pitch of the plurality of elastic wires becomes gradually smaller in a direction from a proximal side of the manipulation wire to the distal side of the manipulation wire, a gap between the plurality of the elastic wires is smaller at a portion between the distal end of the manipulation wire and the maximum outside diameter portion than at a portion between the proximal end side of the manipulation wire and the maximum outside diameter portion, and a tangential line of each of the plurality of elastic wires in the maximum outside diameter portion is inclined at an angle of 45° or less with respect to a plane orthogonal to the central axis without an external force applied to the basket portion, and thereby, when a proximal side of the basket portion is reduced, the maximum outside diameter portion is pushed outward in the radial direction by a first amount which is substantially a same as a second amount by which the proximal side of the basket portion is reduced inward in the radial direction such that an outside diameter of the maximum outside diameter portion is maintained at substantially a same size as the outside diameter before the proximal side of the basket portion is reduced.