There is disclosed a diathermic cutter including a cylindrical main body member having a central axis, an axially elongated member including a tip end portion movable so as to change a projected state from a tip end of the main body member along the central axis of the main body member, an electrode including a base end portion on which the tip end portion of the elongated member is disposed and extending in a direction deviating from the central axis of the elongated member, and an electrically insulating member with which the electrode is coated in such a manner that at least a part of a base-end surface of the base end portion of the electrode in the vicinity of the tip end of the main body member is exposed toward the tip end of the main body member.
