the present invention provides a cathode - ray tube provided with an electron gun capable of emitting electron beams of vertically elongate cross section . a beam control electrode is fabricated by forming beam passage holes in thin portions of a reduced thickness of an electrode plate , and forming excess metal relieving slots on the opposite sides of the beam passage holes , respectively . an electron gun employing the beam control electrode is capable of automatically correcting the cross section of beams so that the beams form substantially circular spots in the periphery of a screen . thus , the deterioration of picture quality attributable to the distortion of the cross section of the beams can be avoided and pictures can be displayed in an improved picture quality .