In this treatment tool for endoscope (1), a sheath (2) includes, at the distal end thereof, a tubular extended part (21a) having a predetermined thickness in the radially outward direction from an inner peripheral face of a first hole (21) and extending further to the distal-end side, and a passive electrode (30) is disposed such as to surround the outer periphery of the extended part (21a). According to the present invention, enough insulation between a high-frequency treatment part (50a) disposed in the first hole (21) and the passive electrode (30) can be secured by a simple configuration.
