PURPOSE: To increase the mechanical strength as well as to enhance the heat dispersion performance by coarsening at least one of the inner and outer surface of the formed shadow mask via the impact of the abrasive grains.

CONSTITUTION: Formed shadow mask 7 is mounted within support mold 9 for the shape protection with exposure being given to inner surface 7a, and minute abrasive grains 11 are sprayed on surface 7a via the blast device to form the coarse surface. Otherwise mask 7 is put over support mold 10 with exposure secured for outer surface 7b, and surface 7b is coarsened by grains 11. In this way, the surface area to be coarsened can be selected freely, and furthermore the intensity and the strength of the heat dispersion can be set freely by selecting the diameter of the grain 11. Thus, the picture quality can be enhanced for the color cathode-ray tube.