An infrared fluorescence observation device includes a light source configured to irradiate visible light and excitation light including a longer wavelength band than the visible light, an imaging unit on which generates a first image on the basis of second light obtained by attenuating a wavelength band including the excitation light from first light emitted from the subject irradiated with at least the excitation light and generates a second image on the basis of third light obtained by eliminating only the wavelength band of the fluorescence including a longer wavelength band than the excitation light from the second light, and a signal processing unit generates a third image according to light of a wavelength band including the fluorescence using the first image and the second image.
