Abstract: In an electron gun assembly of an in-line type, electron beams emitted from cathode pass through first, second and third grid electrodes and are accelerated and controlled by the electrodes. The accelerated and controlled electron beams are converged by a fourth grid electrode structure and are also focused on the phosphor screen by fifth and sixth grid electrodes. The fourth grid electrode structure is comprised of first to third electrode segments having apertures through which electron beams pass. The first and third electrode segments is maintained at a variable potential which is varied in accordance with a deflection of the electron beams and the second electrode segment is maintained at a constant potential.