Described is a ozonizer with a first metal electrode and a second metal electrode with a discharge gap between them, the first electrode being covered with a dielectric. At least the first electrode is designed as an aluminium or aluminium-alloy coating on a glass substrate. The dielectric consists of a thermally sprayed ceramic film, preferably made of .alpha.-aluminium oxide, titanium oxide or hafnium oxide. Also described is a method of manufacturing the ozonizer, the method calling for the ceramic film acting as the dielectric on the first electrode to be applied by thermal spraying. The two electrodes are preferably also produced by thermal spraying. The ozonizer has a particularly high yield, is corrosion-resistant and can be manufactured simply and inexpensively.