A method used to mark a tubular organ of a subject. In a first step, at a position near a lesion on a wall surface of the tubular organ, a first electrode is supplied with high-frequency current, so that the first electrode punctures the wall surface from a surface of a mucosal layer on the wall surface to a predetermined depth. In a second step, the first electrode is supplied with the high-frequency current for a predetermined time such that a first marking is made by cauterization on a muscle layer. In a third step, a second electrode, which is disposed coaxially with the first electrode, is supplied with high-frequency current for a predetermined time such that a second marking is made by cauterization on the surface of the mucosal layer. During the third step, the first electrode is held as is after the second step.
