Proposal is made for providing a high-performance electrode suitable for use in an oxygen-generating electrolytic process having an outstandingly low oxygen overvoltage and exhibiting high durability in a prolonged run of electrolysis. The electrode consists of an electroconductive substrate of a metal, e.g., titanium, and a multiple composite oxide coating layer thereon consisting of at least one layer of type A composed of iridium oxide and tantalum oxide in an Ir:Ta molar ratio of 40:60 to 79.9:20.1 and at least one layer of type B formed on the type A layer composed of iridium oxide and tantalum oxide in an Ir:Ta molar ratio of 80:20 to 99.9:0.1. A plural number of type A layers and a plural number of type B layers can be alternately laid one on the other so as to improve the mechanical stability of the coating layer on the substrate surface.