As a metal compound layer provided between a dielectric and a ground electrode of an ozone generator, there is used a metal compound satisfying the condition (1) the metal compound is not a substance promoting ozone decomposition, the condition (2) the metal compound is not a conductor, the condition (3) the band gap of the metal compound layer is in the range of 2.0 to 4.0 (eV), and the condition (4) the hole potential of a valence band portion formed in the excited state of the metal compound layer is larger than the binding potential (1.25 (eV)) of an oxygen molecule. In addition, as ozone generation processing are executed under an environment in which various ozone decomposition suppression requirements for suppressing a decomposition amount of ozone are imposed on the ozone generator.