Experiments using an ozone generator which has a fine steel wire electrode are described. Various conditions of the wire electrode ozone generator such as wire diameter, volume density of wire electrode, applied voltage and the effects of SF6addition also are reported. The efficiency of the wire electrode ozone generator in air exceeded that of the usual ozone generator for 0.1 mm wire diameter and 0.156 g cm−3volume density of wire over the entire range of applied voltage. This efficiency increases by adding 0.08% SF6in air. Increase of ozone and NOX formation in the air ozone generator can be explained by the reactions of O2and activated N2.