A fluid device assembly (410) has a reservoir tank (402) and a condensation device to coat the surfaces of fine particles. Nozzles to eject a dispersion liquid in which the fine particles (201) are dispersedly suspended are installed in the reservoir tank (402) nearly vertically in order to coat the surfaces of the fine particles (201). The dispersion liquid is ejected downward through the vertically-installed nozzles and the surfaces of the fine particles are coated. Since the dispersion liquid is ejected downward through the nozzles, the fine particles the coating thickness of which is controlled are produced.
