Provided is an endoscope treatment tool of which the usability is favorable regardless of which of a syringe and a water supply tube is used by being connected to a water injection connector. A connector body (18) is connected to an operation part body (22) such that the connector body (18) is rotatable around a rotation axis (28). The operation part body (22) includes a rotation stopper (60) that restricts rotation of the connector body (18). The connector body (18) includes an abutting surface (62) that abuts the rotation stopper (60). The connector body (18) is capable of transitioning between a rotation restricted state, in which the abutting surface (62) abuts the rotation stopper (60) such that rotation of the connector body (18) in one direction is restricted, and a rotation allowed state, in which the abutting surface (62) abutting the rotation stopper (60) is released and rotation of the connector body (18) in both directions is allowed, by rotating with respect to the operation part body (22).