Provided is a slit lamp microscope capable of controlling irradiation of slit light and background illumination light interlockingly. Embodiment includes a main illumination system, background illumination system, observation system and controller. The main illumination system includes a first light source unit that outputs first light and slit forming unit that forms a slit with changeable width, and illuminates an eye with the first light having passed through the slit. The background illumination system includes a second light source unit that outputs second light, and illuminates a peripheral area of an eye area irradiated with the first light. The observation system includes an eyepiece lens, imaging device, and group of optical elements that guides reflected light of the first light and reflected light of the second light from the eye to the eyepiece lens and imaging device. The controller interlockingly controls the main illumination system and second light source unit.