In a spectrometry device, a control unit controls a light source so that input of excitation light to an internal space is maintained in a first period, and that the input of the excitation light to the internal space is stopped in a second period, and the analysis unit calculates the photoluminescence quantum yield of a long afterglow emission material on the basis of the number of absorbed photons of the long afterglow emission material obtained on the basis of excitation light spectral data in the first period and the number of light emission photons of the long afterglow emission material obtained on the basis of light emission spectral data in any of the first period, the second period, and a total period of the first period and the second period.