PURPOSE: To eliminate the entanglement of a color selective electrode, which is made of narrow cable element, of a color cathode-ray tube by radiating the electron beam so as to concentrate on a part, where the entanglement is generated, to lower the tension of the narrow cable elements, and thereafter, vibrating a cathode-ray tube light.

CONSTITUTION: The image signal 23 such as a window pattern for radiating the electron beam so as to concentrate on a tangled part 21 of a color selective electrode 11, which is made of mesh element, is given from an image signal generating device 22 to a color cathode-ray tube 10. Tension of the tangled part 21 is thereby lowered to facilitate the movement of the tangled part 21 by vibrating from the outside. Under this condition, when the color cathode-ray tube 10 is vibrated lightly, the tangled part 21 gets loose, and the entanglement is eliminated. Consequently, the entanglement is thereby eliminated easily to obtain the fine image quality.