Provided is an ablation device including a narrow insertion section insertable into a body, a distal end section provided at a distal end of the insertion section and having a narrow cauterizing surface that is formed in a longitudinal direction in one area in a circumferential direction and that releases energy to biological tissue, and a radiopaque marking section provided at the distal end section and substantially parallel to the cauterizing surface. The marking section has a three-dimensional shape such that projection shapes obtained when projected from different sides in a radial direction of the distal end section are different from each other.
