PURPOSE: To surely carry out accurate coloration any time and finish up finely by sticking a adhesive double coated sheet parts with prescribed shapes for masking to an automotive body side from a peeling liner along the cut line, winding up the part for masking and then carrying out spray-painting, and carrying out painting of each color in the same manner as needed.

CONSTITUTION: The upper end of a material 7 for masking is fixed at the set position of the side face 4 of an automotive body and at every painting time of each color, the adhesive double coated sheet parts 5a, 5b, 5c with prescribed shapes for masking are stucked to the side face 4 from a peeling liner 6 along the cut lines 13, 14 in the order corresponding to the spray-painting order of each color while the material 7 for masking is hung vertically. Consequently, in the case a plurality of cut lines 13, 14 corresponding to a plurality of the masking shapes such as designs and patterns with a plurality of colors necessary for the spray-painting are formed previously on the same masking material 7, the adhesive double coated sheet parts 5a, 5b, 5c with the prescribed shapes for masking are always stuck to the correct positions with the desired designs and patterns for masking for each painting.