A chemical sensor element contains a resonator having a first reflector in which particles of a fine metal structure are arranged two-dimensionally and periodically is counterposed with interposition of a dielectric layer to a second reflector, wherein the resonance wavelength of a resonator in which the entire of the first reflector is replaced by a metal thin film having the same thickness as the metal fine structure is different from the surface plasmon resonance wavelength induced in the metal fine structure; and the mode of the surface plasmon resonance excited in the metal fine structure is coupled with the mode of the resonator in which the entire of the first reflector is replaced by the metal thin film.