The invention aims at providing a dielectric film having a low dielectric constant and enhanced mechanical strength. A surfactant and an silica derivative are dissolved into a solvent at a desired mole ratio. The precursor solution is applied over the substrate, and the substrate is exposed to a silica derivative atmosphere before being sintered, thereby supplying a silica derivative. Thus, contraction of the film stemming from hydrolysis is inhibited, and a sturdy mesoporous silica thin film which takes the self-assembly of the surfactant as a mold is obtained while cavities are maintained intact without being fractured. Thus, there is formed an inorganic dielectric film which is formed on the surface of the substrate and has a cyclic porous structure including layered or columnar pores oriented so as to become parallel with the surface of the substrate.