A color cathode ray tube includes a three-beam in-line type electron gun. The main lens section includes a focus electrode and an anode facing the focus electrode, each of the focus electrode and the anode has an electrode having a single opening common for three electron beams in an end thereof facing each other and a plate electrode disposed therein and having beam apertures. The focus electrode and the anode satisfy a following inequality:(A+566)/106>H-2.times.Swhere A is V1.times.V2.times.T, V1 is a vertical diameter of the single opening, V2 is a vertical diameter of a center one of the beam apertures and T is an axial distance between the single opening and the plate electrode, H is a horizontal diameter of the single opening, S is P.times.L/Q, P is a horizontal center-to-center spacing between adjacent phosphor elements at a center of the three-color phosphor screen, Q is an axial spacing between the three-color phosphor screen and the shadow mask at the center of the three-color phosphor screen, and L is an axial distance between the shadow mask and the single opening in the focus electrode.