A forming apparatus of a thin film includes a processing chamber where a predetermined process is carried out on a surface of a supplied substrate. A feeding device is provided in the processing chamber for feeding material to form an organic molecular layer including silicon or germanium on the surface of the substrate. A forming method of a thin film includes the steps of forming the thin film on the surface of the supplied substrate in the processing chamber, and feeding material for forming the organic molecular layer, including silicon or germanium, on the formed thin film on the surface of the substrate through a feeding device in the processing chamber, and then forming the organic molecular layer on the surface of the substrate.