A treatment tool for an endoscope, having a flexible sheath being made of electrically insulating material to be inserted through an instrument channel of the endoscope, an operation wire, which is adapted to be advanced and retracted in an axial direction of the sheath inside the sheath, a treatment instrument, which is arranged at a distal portion of the treatment tool and is adapted to be protruded and retracted from a distal end of the sheath, and a fluid channel with an opening, through which fluid is ejected toward the treatment instrument, is provided. The operation wire and the fluid channel are arranged inside the sheath in parallel with an axis of the sheath. The treatment instrument is connected to the operation wire in a laterally displaced position with respect to the operation wire, and is arranged in front of the opening of the fluid channel.