A measuring device includes a light-emitting unit that radiates light onto an object, a first lens that changes a divergence degree of the light, a diaphragm having an aperture that reduces a diameter of the light, a second lens that converges and radiates the light onto the object, a light-receiving unit that receives at least part of the light that has been reflected by the object and that has passed through the second lens, a measuring unit that measures the object by using results related to the light-receiving unit, a reflector whose angle with respect to the light is adjustable, and a correction unit that varies a light-receiving position on the light-receiving unit by varying the reflector's angle and corrects a light amount of the light-emitting unit and a sensitivity of the light-receiving unit by using results obtained at each light-receiving position.