A field emission cathode having an emitter provided with a sharp point for emission of electrons and a controlling gate electrode is composed of a supporting substrate, an emitter material layer formed of an emitter material, superposed on and attached fast to the supporting substrate, and provided with an emitter hole, an insulator layer so formed on the surface of the emitter material layer as to expose the tip part of the emitter projection therethrough, and an impurity diffusion layer formed on the surface of the insulator layer and enabled to function as an etching stopper layer.