Provided is a fluorescence observation apparatus (100) including a light source (3) that radiates illumination light and excitation light onto a subject a return-light-image generating portion (61) and a fluorescence-image generating portion (62) that generate a return-light image (G1) and a fluorescence image (G2) of the subject, respectively a fluorescence detecting portion (63) that detects a fluorescence region in the fluorescence image (G2) a return-light-image adjusting portion (65) that adjusts gradation values of the return-light image (G1) a superimposed-image generating portion (66) that generates a superimposed image (G3) by using the return-light image (G1), in which the gradation values have been adjusted, and the fluorescence image (G2) and a coefficient setting portion (64) that sets, in the case in which the fluorescence region is detected by the fluorescence detecting portion (63), a degree-of-adjustment, by which the gradation values of the return-light image (G1) are adjusted by the return-light-image adjusting portion (65), so that the gradation values of the return-light image (G1) are decreased as compared with the case in which the fluorescence region is not detected by the fluorescence detecting portion (63).
