To accurately obtain fluorescence intensity in a variable passband. Provided is a fluorescence observation apparatus (1) including an excitation light source that emits excitation light a Fabry-Perot resonator (13) including a variable passband in which the wavelength of light that passes therethrough changes with changes in distance between the surfaces of optical members (13a and 13b) opposing each other with a distance therebetween, a fixed passband in which the wavelength of light that passes therethrough does not change irrespective of changes in the distance between the surfaces, and a transition band therebetween an excitation-light cut filter (12) that blocks passage of the excitation light a band cut filter (20) having a cut-off band including the transition band and not including the wavelength of the excitation light and a photodetector (14) that detects fluorescence that has passed through the Fabry-Perot resonator (13), the excitation-light cut filter (12), and the band cut filter (20).
