The cathode electrode assembly of an electron gun assembly comprises an inner cathode cylinder supporting a base metal coated with an electron emitting material and an outer cathode cylinder coaxially supporting said inner cathode cylinder. Said outer cathode cylinder is supported at a first supporting point by a cathode holder fitted over said outer cathode cylinder. Said cathode holder is supported at a second supporting point by an electrode supporting piece supported by an insulating support pillar. Respective portions of the outer cathode cylinder and cathode holder are formed of the same quality of material.
