PURPOSE: To obtain the ozonizer without generating the impurities unsuitable for a semiconductor by using parallel plates as discharge surfaces, and supplying O2 or air into the gap between the discharge surfaces as the raw gas.

CONSTITUTION: Thin quartz plates 1 and 1' are closely attached to an electrode plate 3 respectively through conductive adhesives 2 and 2'. A narrow discharge space 5 is formed between the plates 1 and 1' by a spacer 4 of 'Teflon(R)'. The raw gas is supplied through a pipe 6, and passed through the space 5. A discharge power is supplied between the high-permittivity plates 1 and 1' by the high voltage impressed on the electrode plates 3 and 3', and O3 is generated. The generated O3 is supplied to a desired place through a pipe 7. At this time, the electrode plates 3 and 3' are cooled by a refrigerant 8 such as CFC, hence a temp. rise is prevented, and concd. O3 is obtained.