To provide an art achieving a high detection efficiency to fluorescence and cutoff of return light.

A fluorescence microscope 1 detects, by a photodetector 13, fluorescence L2 from a sample S excited by excitation light L1 emitted from a light source 2, via a dichroic mirror 6, polarization plane rotating means 7, and a wavelength-selective filter 11. The dichroic mirror 6 is disposed in an optical path extending from the light source 2 to the sample S, and has such wavelength characteristics as reflecting at least an S-polarized component of the excitation light and transmitting the fluorescence. The wavelength-selective filter 11 is disposed between the photodetector 13 and the dichroic mirror 6 and has such wavelength characteristics as reflecting at least the S-polarized component of the excitation light and transmitting the fluorescence. The fluorescence microscope 1 is so configured that the light entering and transmitted through the dichroic mirror 6 as P-polarized light enters the wavelength-selective filter 11 as the S-polarized light so as to cut off the return light, or the excitation light progressing from the sample S towards the photodetector 13.