A cathode structure comprises a cylindrical metal sleeve having aperture portions at both ends, a base metal having an aperture portion on one end, which is fitted onto one of the aperture portions of the metal sleeve, and an electron-emitting layer, which is formed on a flat portion of an outside surface of the base metal. After an electron-emitting material is sprayed onto the base metal, its surface is mechanically flattened to form the electron-emitting layer. Thus, the planarity of the surface of the electron-emitting layer can be improved without deterioration of the electron emission characteristics and the moirnull can be decreased without reduction of the resolution.