To prevent the deposition of manganese dioxide and/or the corrosion of a titanium support by allowing an anode to contain a titanium support having an electrocatalytic film and allowing the electrocatalytic film to use the oxides of iridium and bismuth as a base.

Preferably, the electrocatalytic film moreover contains the oxides of any of the group IVA, VA and VB metals of tin, antimony, tantalum and niobium, bismuth and iridium are used as the main components, and the tin, antimony and niobium are small amounts of components. The content of iridium lies in the range of 55 to 80%, preferably of 60 to 65%, the content of bismuth lies in the range of 45 to 20%, preferably of 40 to 25%, the contents of antimony and tin lie in the range of 2.5 to 10%, preferably of 5%, and the contents of tantalum and niobium lie in the range or 2.5 to 7.5%, preferably of 5%. Nonconducting bismuth oxide stabilizes iridium oxide as an electric conductor and also as a catalyst for generating oxygen.