PURPOSE: To improve the voltage resistant quality of a color Braun tube by subjecting the tube to high voltage treatment, and then vapordepositioning a conductive film on the inner wall of the neck of the tube by subjecting a shielding electrode to dielectric heating.

CONSTITUTION: During the process of voltage-proof treatment, the electric potential distribution of the inner wall of a neck 16 is represented by both a curve (a) which indicates the electric potentials of an inner conductive film 15, and a curve (b) which has an ideal slant and indicates the electric potentials of a part of the inner wall of the neck 16, which is uncoated with the film 15 and extends up to a stem part. Therefore, the high-voltage treatments of the fifth to the first grids 10, 9, 8, 7 and 6 and a cathode 5, which are medium to low voltage electrodes, also are completely carried out. After such high voltage treatments are performed, a shielding electrode 9a is subjected to dielectric heating so as to make a conductive film 9b to be vapordeposited on the inner wall of the neck 16 so that the film 9b corresponds to the electrode 9a. As a result, the electric potential distribution of the inner wall of the neck 16 comes to be represented by a curve (a1) which indicates the electric potentials of the inner conductive film 15, and a curve (b1) which indicates the slant of the electric potentials of a part of the inner wall of the neck 16, which extends from the end of the film 15 through the conductive film 9b toward the stem part. Consequently, the voltage resistant characteristic of the color picture tube is improved.