To accomplish write-once type optical recording mediums that have excellent recording and reproducing characteristics and producibility and that are capable of being fabricated at low cost. A write-once type optical recording medium 10 has the structure of which an inorganic recording film 6, a dielectric film 4, and a light transmission layer 5 have been successively formed on a substrate 1. The inorganic recording film 6 is composed of a metal film 2 and an oxide film 3 successively formed on the substrate 1. When light is radiated to the inorganic recording film 6, oxygen is separated from the oxide film 3 due to the light catalyst effect, resulting in increasing the oxygen concentration on the metal film 2 side and largely varying the optical constant.