A field emission cathode of the present invention is characterized by the possession of a special layer which is adsorbed onto the surfaces of a tip that is joined to the top of a hairpin-shaped filament.This layer is formed by adsorbing a selected metal via oxygen to a thickness which does not exceed the thickness of the monolayer of atoms.The metal will be selected from chromium, aluminum, cerium, magnesium, titanium, silicon, zirconium or hafnium.The field emission cathode features that the electrons are emitted in a concentrated manner from a particular crystal plane among the crystal planes of the tip.Therefore, it is possible to obtain a field emission cathode having very small emission angle of electrons.