An optical scanning device includes: a light projector configured to radiate light while causing the light to make angular movement at a constant speed; and a light reflector configured to reflect the light radiated from the light projector to guide the light to an intended irradiated point on a predetermined scanning line. The light reflector includes a plurality of reflecting portions and reflects, at least twice, the light radiated from the light projector to guide the light to the intended irradiated point. The reflecting portions each include a plurality of reflecting surfaces. A length of an optical path from the light projector to the irradiated point is substantially constant for all of irradiated points on the scanning line, and a scanning speed, on the scanning line, of the light radiated from the light projector is substantially constant.