An ozone−processing device for forming or modifying an oxide film or removing a resist film by spraying an ozone gas against a semiconductor substrate or liquid crystal substrate. An ozone−processing device (1) comprises a stage (20) on which a substrate (K) is placed, a heater for heating the substrate (K) on the stage (20), opposed plates (40) opposed to the opposite surface of the substrate (K), having a nozzle open to the opposite surface of the substrate (K), and used for spraying an ozone gas against the substrate (K), and a gas supply (60) for supplying an ozone gas to the nozzles of the opposed plates (40) to eject the ozone gas. The opposed plates (40) are so arranged in the same plane as to be spaced from one another to form gaps therebetween. The volume of each opposed plate (40) is small. As a result, even if heat is transferred between the opposed plates (40) and the substrate (K), the opposed plates (40) and the substrate (K) come into a heat−balanced state in a short time, thereby facilitating the temperature control of the substrate (K).