A treatment tool for an endoscope, comprising: a sheath; a balloon provided at a distal end of the sheath, formed of a film of a transparent material, and configured to be expandable from a folded initial shape to an unfolded inflated shape; an inner shaft connected to the distal end of the sheath and configured to protrude from a distal end of the balloon through an inside of the balloon; a middle marker configured to indicate a middle position of the balloon in a direction of a length of the balloon; and at least one or more positioning markers (7, 7a, 7b, 7c) provided on the inner shaft independently of the middle marker and configured to be visible through the film of the balloon, wherein the balloon has: a proximal end-side region which is positioned at a proximal end part of the balloon and inflation of which is initiated when an internal pressure of the balloon is a first internal pressure value; a distal end-side region which is positioned at a distal end part of the balloon and inflation of which is initiated when the internal pressure of the balloon is the first internal pressure value; and a middle part that is provided between the proximal end-side region and the distal end-side region, wherein when the internal pressure of the balloon is a first internal pressure value, the proximal end-side region and the distal end-side region undergo faster progress of unfolding than the middle part, and thereby the proximal end-side region and the distal end-side region have a larger diameter than the middle part, and when the internal pressure of the balloon is a second internal pressure value greater than the first internal pressure value, the proximal end-side region, the distal end-side region, and the middle part are deformed to the inflated shape, and a diameter of the middle part is configured to be substantially the same as those of the proximal end-side region and the distal end-side region, and wherein the positioning marker positioned at a most distal end is provided at a position corresponding to a predetermined range close to a proximal end from a boundary between the middle part and the proximal end-side region at a side closer to the proximal end than the middle part in a direction of a longitudinal axis of the inner shaft. a sheath; a balloon provided at a distal end of the sheath, formed of a film of a transparent material, and configured to be expandable from a folded initial shape to an unfolded inflated shape; an inner shaft connected to the distal end of the sheath and configured to protrude from a distal end of the balloon through an inside of the balloon; a middle marker configured to indicate a middle position of the balloon in a direction of a length of the balloon; and at least one or more positioning markers (7, 7a, 7b, 7c) provided on the inner shaft independently of the middle marker and configured to be visible through the film of the balloon, wherein the balloon has: a proximal end-side region which is positioned at a proximal end part of the balloon and inflation of which is initiated when an internal pressure of the balloon is a first internal pressure value; a distal end-side region which is positioned at a distal end part of the balloon and inflation of which is initiated when the internal pressure of the balloon is the first internal pressure value; and a middle part that is provided between the proximal end-side region and the distal end-side region, a proximal end-side region which is positioned at a proximal end part of the balloon and inflation of which is initiated when an internal pressure of the balloon is a first internal pressure value; a distal end-side region which is positioned at a distal end part of the balloon and inflation of which is initiated when the internal pressure of the balloon is the first internal pressure value; and a middle part that is provided between the proximal end-side region and the distal end-side region, wherein when the internal pressure of the balloon is a first internal pressure value, the proximal end-side region and the distal end-side region undergo faster progress of unfolding than the middle part, and thereby the proximal end-side region and the distal end-side region have a larger diameter than the middle part, and when the internal pressure of the balloon is a second internal pressure value greater than the first internal pressure value, the proximal end-side region, the distal end-side region, and the middle part are deformed to the inflated shape, and a diameter of the middle part is configured to be substantially the same as those of the proximal end-side region and the distal end-side region, and wherein the positioning marker positioned at a most distal end is provided at a position corresponding to a predetermined range close to a proximal end from a boundary between the middle part and the proximal end-side region at a side closer to the proximal end than the middle part in a direction of a longitudinal axis of the inner shaft.