PURPOSE: To improve the shapes of beam spots over the entire surface of a fluorescent screen, and increase the resolution and improve the uniformity of the focus quality of an in-line-type color picture tube by providing asymmetrical lenses, which make the sectional shapes of electron beams incident upon main lenses laterally oblong, in the midst of electron-beam paths in front of the said main lenses.

CONSTITUTION: A bipotential-type electron gun is constituted of three cathodes 9, 10 and 11 arranged on a horizontal line, a G1 electrode 12 having vertically- oblong slot-like beam-passing holes 13, 14 and 15, a G2 electrode 16 having circular beam-passing holes 17, 18 and 19, a box-like G3 electrode 20 and a box- like G4 electrode 31. Electron beams discharged from the cathodes 9, 10 and 11 come to have laterally-oblong sectional shapes by means of asymmetrical lenses developed by the beam-passing holes 13, 14 and 15 of the electrode 12, and become incident upon main lenses. When such electron beams having laterally- oblong sectional shapes are transmitted by the main lenses, the shapes of beam spots formed on a fluorescent screen are extremely improved from those obtained by use of electron beams with circular sections, and the diameters of the spots become small.