An in-line three beam electron gun for a color cathode ray tube comprising a cathode for emitting electron beams, a control electrode and a screen electrode, first through fourth focusing electrodes and an accelerating electrode, wherein the third focusing electrode has vertically elongated electron beam apertures to form a quadrupole lens, and the fourth focusing electrode has circular electron beam apertures. A first uni-potential lens is formed between the first and second focusing electrodes, a second uni-potential lens is formed between the second and third focusing electrodes, a quadrupole lens is formed between the third and fourth focusing electrodes and a main leans is formed between the fourth electrode and the accelerating electrode, when a static voltage is applied to the first and second focusing electrodes and a dynamic focusing voltage synchronous to a deflection signal is applied to the third and fourth focusing electrodes.