In a film forming method, in a state where a metal solution is sealed in a first accommodation chamber of a housing with a solid electrolyte membrane and a fluid is sealed in a second accommodation chamber of a placing table with a thin film, a substrate is placed on the placing table and the placing table and the housing are moved relative to each other to cause the substrate to be interposed between the solid electrolyte membrane and the thin film, the solid electrolyte membrane and the thin film are pressed against the substrate interposed therebetween to cause the solid electrolyte membrane and the thin film to conform to a surface and a rear surface of the substrate, thereby forming a metal film.