The light emission analyzing device includes: a first light intensity calculation unit that performs polynomial approximation on a spectroscopic spectrum indicating a light intensity for each wavelength in a container as measured by a spectrometer so as to calculate the light intensity; a second light intensity calculation unit that subtracts, for each wavelength, the light intensity calculated by the first light intensity calculation unit from the light intensity indicated by the spectroscopic spectrum measured by the spectrometer so as to calculate a light intensity corresponding to a bright-line spectrum of a molecule; and a ratio calculation unit that calculates, by using the light intensity calculated by the second light intensity calculation unit, a ratio between (a) a peak value of a molecular spectrum of a first molecule and (b) a peak value of a molecular spectrum of a second molecule.