An image scanning device includes lighting circuits; a light source including light-emitting elements arranged in a line such that the light-emitting elements connected in series to the same lighting circuit are not positioned adjacent to each other; a reflecting part; a photoelectric conversion unit photoelectrically converting reflected light from the reflecting part; a lighting control unit selectively turning on one of the lighting circuits; a memory storing an area information table containing information on main-scanning areas of the photoelectric conversion unit in association with identification information of the lighting circuits; and a failure determining unit identifying the main-scanning areas corresponding to the identification information of the turned-on lighting circuit by referring to the area information table and comparing intensities of the reflected light entering the identified main-scanning areas with a first threshold to determine whether the light-emitting elements connected to the turned-on lighting circuit are at fault.