Oxidation treatment is performed to the surface of a substrate provided with a photocatalytic conductive film and an insulating film; treatment with a silane coupling agent is performed, so that a silane coupling agent film is formed and the surface of the substrate is modified to be liquid-repellent; and the surface of the substrate is irradiated with light of a wavelength (less than to equal to 390 nm) which has energy of greater than or equal to a band gap of a material for forming the photocatalytic conductive film, so that only the silane coupling agent film over the surface of the photocatalytic conductive film is decomposed and the surface of the photocatalytic conductive film can be modified to be lyophilic.