PURPOSE: To enable carving having a colorful variation, by so constituting that a pattern of a block copy painted by making use of colors other than black and white is carvable on a material to be processed by sand blast processing over exact display of a difference of lightness of the colors.

CONSTITUTION: A flowery pattern with trimming painted on a block copy 1 is painted separately in white parts 2, black parts 3 and medium lightness parts 4, in sand blast processing which is carried out by applying a masking sheet fabricated by making use of photosensitive resin to a work. A photograph of lightness of the block copy 1 is taken in a dissolved dot formation, through which a halftone negative film of a dotted screen is made and then the masking sheet is fabricated by removing an unexposed photosensitive resin through this film. Then, the sand blast processing is carried out by applying the masking sheet to a material to be processed. Carving having a colorful variation can be done in this way.