To eliminate an abnormal discharge in an ozone generating vessel and to increase the yield of ozone in the nonequilibrium plasma discharge ozonizer formed by providing a high-voltage glectrode in the vessel and furnishing a grounded electrode tube in the coaxial peripheral part of the high-voltage electrode through a discharge space and impressing a pulse voltage having a sharp leading edge and a short duration to generate ozone in a raw gas circulated in the discharge space.

The insulator supporting plates 25a and 25b having raw gas circulating holes 27a to 27h are provided outside the discharge space 3 in a vessel 1, namely on both end sides of a grounded electrode tube 2, a high-voltage electrode 4 is allowed to pierce the center to support the electrode 4, and the ends are firmly attached to the spacers 26a to 26h. Consequently, the supporting plates 25a and 25b are not exposed to the high electric field of the discharge space 3, an abnormal discharge is hardly generated, the discharge is stabilized, and the yield of ozone per unit area of the electrode is increased.