A color cathode-ray tube apparatus comprises an electron gun structure for generating three electron beams arranged in line, the three electron beams comprising a center beam and a pair of side beams. The electron gun structure forms a main lens for ultimately focusing the three electron beams on a phosphor screen. The main lens is formed by a focus electrode, an additional electrode and an anode electrode which are arranged in a direction of traveling of electron beams. A voltage application unit applies a voltage to each of the electrodes such that a voltage higher than a voltage applied to the focus electrode and lower than a voltage applied to the anode electrode is applied to the additional electrode, and in synchronism with deflection of the three electron beams by the deflection yoke, a value S varies: S=[(applied voltage to the additional electrode)-(applied voltage to the focus electrode)]/[(applied voltage to the anode electrode)-(applied voltage to the focus electrode)]. An angle of emission of each of the side beams emanating from the main lens varies in synchronism with a variation of the value S.