In an in-line electron gun, three apertures, closer to an accelerating electrode, of a focusing electrode, which forms three main electron lenses, are defined by bridging with a partition electrode means two neck portions of a peanut-shaped aperture consisting of a center or inner aperture and two outer apertures which partially overlap the center or inner aperture and are contiguous therewith, thus forming a continuous aperture in the form of a peanut pod having three seeds.