PURPOSE: To provide a simple mechanism corresponding to a dustproof coating method in which adhesion of dust in the coating work is held at a minimum and readjustment work is simplified and labor saving is permitted.

CONSTITUTION: In the case of performing specular finish coating in the coating work, it is ideal that a dustless state is endlessly continued. In order to prevent adhesion of dust by a dustproof coating method of a simple mechanism in, a spray booth provided in sheet metal-coating work of a small business, a bonnet-holding device 2 of a rotary and stationary mechanism is fitted to a stand device 1 and fixed. The stand device 1 is formed, so that undercoating is performed in a position and an angle in which dust is difficult to be stuck and the undercoating is inverted and directed to the rear and dried after finish coating to prevent dust from being stuck in a time for drying.