Two sprayer units are arranged along a conveyer. A coating surface of a panel conveyed by the conveyer is divided into four coating areas. Then, the sprayer units reciprocate parallel to the conveying direction and coat the individual coating areas. At this time, at the boundaries of the coating areas, the positions of the turning paths for reciprocation of the sprayer units are shifted from the front side to the rear side in the conveying direction and step-like coating trajectories are formed. As a result, the size of the area coated by each of the sprayer units can be expanded.