To provide a microscope that prevents variation in brightness of a transmitted image even when the brightness of a fluorescent image is adjusted.

The microscope includes: an excitation light source 2 that emits excitation light; an illuminating optical system 3 that irradiates a specimen A with excitation light from the excitation light source 2; a fluorescence detecting optical system 4 that detects fluorescence emitted from the specimen A; a transmitted-light detecting optical system 5 that detects excitation light passed through the specimen A; and a control device 6 that adjusts the sensitivity of the transmitted-light detecting optical system 5 on the basis of the intensity of excitation light emitted from the excitation light source 2.