A microscope comprising: an optical device; and a microscope main body, wherein the optical device comprises: a laser light source; an optical system that transmits laser light emitted from the laser light source, wherein the optical system comprises a reflected-light generator (8, 11) configured to reflect a part of the transmitted laser-light, wherein a beam-shaping optical system or a collimator optical system acts as the reflected light generator; and a polarization-dependent element (9, 32) into which the laser light transmitted by the optical system enters, characteristics of outgoing light being changed according to a polarization state of the incident light, wherein the optical system comprises: a first λ/4 wave plate disposed between the laser light source and the reflected-light generator (8, 11); and a second λ/4 wave plate configured to be fixed so as to maintain a relative direction around an optical axis with respect to the first λ/4 wave plate, and the second λ/4 wave plate disposed between the reflected-light generator (8, 11) and the polarization-dependent element (9; 32), wherein the laser light emitted from the second λ/4 wave plate plate is a linearly polarized light, wherein the microscope main body comprises: a scanner that scans laser light emitted from the second λ/4 plate and having passed through the polarization-dependent element (9, 32) two-dimensionally; and a photodetector that detects light from a specimen, wherein a specimen image is acquired according to signals from the photodetector. an optical device; and a microscope main body, a laser light source; an optical system that transmits laser light emitted from the laser light source, wherein the optical system comprises a reflected-light generator (8, 11) configured to reflect a part of the transmitted laser-light, wherein a beam-shaping optical system or a collimator optical system acts as the reflected light generator; and a polarization-dependent element (9, 32) into which the laser light transmitted by the optical system enters, characteristics of outgoing light being changed according to a polarization state of the incident light, wherein the optical system comprises: a first λ/4 wave plate disposed between the laser light source and the reflected-light generator (8, 11); and a second λ/4 wave plate configured to be fixed so as to maintain a relative direction around an optical axis with respect to the first λ/4 wave plate, and the second λ/4 wave plate disposed between the reflected-light generator (8, 11) and the polarization-dependent element (9; 32), wherein the laser light emitted from the second λ/4 wave plate plate is a linearly polarized light, wherein the microscope main body comprises: a scanner that scans laser light emitted from the second λ/4 plate and having passed through the polarization-dependent element (9, 32) two-dimensionally; and a photodetector that detects light from a specimen, wherein a specimen image is acquired according to signals from the photodetector. a scanner that scans laser light emitted from the second λ/4 plate and having passed through the polarization-dependent element (9, 32) two-dimensionally; and a photodetector that detects light from a specimen, wherein a specimen image is acquired according to signals from the photodetector.