In a coating method, such as a droplet discharge method which requires baking, it is an object of the present invention to reduce the baking temperature at the time of forming a wiring and a conductive film. As a feature of the present invention, a composition, in which nanoparticles of a conductive material are dispersed in a solvent, is discharged using a droplet discharge method, and then dried to vaporize the solvent. Then, pretreatment using active oxygen is performed. After which, baking is then performed, whereby a wiring and a conductive film are formed. By performance of the pretreatment by active oxygen before the baking, a baking temperature at the time of forming the wiring and conductive film can be reduced.