A new electrochemical ozone generator which has a proton exchange polymer membrane as an electrolyte, pure water as a source material and an oxygen diffusion electrode as a cathode was proposed to eliminate hydrogen evolution on the cathode and also to reduce electrolytic power consumption. The device was evaluated under varied operating conditions changing current density, temperature and oxygen flow rate. The water permeable high performance gas electrode enabled current density operation over 1.0 A cm-2 without generating hydrogen gas in the cathode side outlet gas. The power consumption was successfully reduced to two thirds of that of the hydrogen evolution type electrolyzer over a period of three months’ operation.