A positive electrode for a lithium ion battery has a conductive collector, a positive electrode active material layer being contact with the collector, and a cover layer disposed on at least part of the surface of the positive electrode active material layer. The positive electrode active material layer has a compound containing at least one kind selected from a group of cobalt, nickel, and manganese as a component. The cover layer is made of a compound with lithium ion conductivity that is expressed by general formula Li.sub.xPT.sub.yO.sub.z or Li.sub.aMO.sub.bN.sub.c and has high moisture resistance.