Observation is performed at a more appropriate sensitivity without causing deterioration of the image quality. Provided is a fluorescence observation apparatus including an excitation light source that emits excitation light to be radiated onto an imaging subject a fluorescence-image acquisition portion that is provided with an imaging device that acquires fluorescence images by capturing fluorescence generated at the imaging subject due to the irradiation with the excitation light emitted from the excitation light source and a sensitivity adjusting portion that adjusts an number of pixels for binning summing and/or an exposure time for the imaging device on the basis of luminance information of the fluorescence image acquired by the imaging device of the fluorescence-image acquisition portion so that an SN ratio of the fluorescence image becomes equal to or higher than a predetermined threshold.
