A spectroscopic analysis device includes a detector and a processor. The detector detects measurement light obtained by irradiating, with irradiation light, a sample that contains a contained substance disposed on a film on which surface plasmons are generated. The measurement light includes information on an optical spectrum of the sample, and the information includes a resonance spectrum of the surface plasmons and an absorption spectrum of the sample. The processor calculates: a peak wavelength in a wavelength band in which the resonance spectrum and the absorption spectrum are generated; a peak absorbance of the contained substance based on an absorption band of the contained substance; and a ratio of the contained substance to the sample based on the peak wavelength and the peak absorbance.