PURPOSE: To enable the spherical portion to be bulged smoothly and effectively, by cutting off the upper edge of the die thereby providing at least two stepped portions there.

CONSTITUTION: The upper edge portion of the die 14 is cut off so that a recess portion is provided, and thereby a stepped portion 34 and a lower stepped portion 35 are provided, on the reducing surface 18 of the die 14. The portion 42 of a blank to become the mask skirt portion is clamped and pressed by the die 14 and the blank holder 23, and the punch 28 is pushed inwardly of the die 14 down to the level of the lower stepped portion 35, whereby the shadow mask blank 41 is processed so that the spherical portion 43 is smoothly bulged. The blank 41 is effectively elongated by smoothly acting tension exerted thereon in the rather large void space formed at the upper portion of the die 14 between the upper cut-off surface 37 and the punch 28. Then the punch 28 is further pushed down along the reducing surface 18 of the die 14, with the pressure by the die 14 and the blank holder 23 released, whereby the portion 42 to become the mask skirt portion is processed by reducing.