An apparatus for painting articles comprises a painting booth delimited by side walls and having at least one inlet opening and an outlet opening reciprocally aligned on two of said respectively opposite side walls. A transport assembly moves a plurality of articles being processed respectively aligned along a movement path extending through the painting booth, to lead the articles being processed therein through the inlet opening and to extract said articles through the outlet opening. The delivery nozzles operatively arranged inside the painting booth deliver atomised paint against the articles transported along the movement path. Adjustment devices comprising adjustment knobs positioned externally of the painting booth and manually accessible by an operator operate on each delivery nozzle to modify its positioning with respect to the articles being processed.