Provided is a high-frequency treatment tool including: a sheath having an inner hole that passes therethrough in a longitudinal direction; a first electrode portion that is formed in a rod shape, that passes through the inner hole of the sheath to protrude from a distal end of the sheath, and that is configured to apply a high-frequency current; a second electrode portion that is disposed at a position at which the second electrode portion is electrically connected with the first electrode portion; and a power source that uses the first electrode portion as a negative electrode, that uses the second electrode portion as a positive electrode, and that supply a current between the first electrode portion and the second electrode portion so that a state in which attached matter attached to the first electrode portion is lifted from the first electrode portion due to osmosis is created.