In general, an ozone generating apparatus comprises a dielectric tube made of a dielectric such as glass. On the inner surface of the dielectric tube, an electrically conductive film as a first electrode is formed and constitutes a dielectric electrode together with the dielectric tube. Outside the dielectric tube, a second, hollow cylindrical electrode is provided, surrounding the first electrode. Spacers are inserted between the dielectric tube and the second electrode, forming a small discharge gap. A silent discharge is generated in the discharge gap by allowing a feed gas containing oxygen gas to flow through the discharge gap, while applying a high voltage across the first and second electrodes. The oxygen contained in the feed gas is ozonized by the silent discharge, producing an ozonized gas.
In the ozone generating apparatus described above, high ozone generating efficiency may be achieved by shortening the distance between the dielectric tube and the second electrode (discharge gap length). However, if the discharge gap length is made too short, it becomes difficult to uniformly maintain the discharge gap, failing to achieve uniform discharge. Therefore, in the conventional ozone generating apparatus, the discharge gap length has been set at 0.6 mm to 1 mm.