An optical scanner used for an image-forming device to form a color image includes a plurality of photosensitive drums for superimposing a developer image formed on each of the plurality of photosensitive drums. The optical scanner includes a casing, a plurality of light sources, a deflector, an optical system, and a storage device. The plurality of light sources is provided in a one-to-one correspondence with the plurality of photosensitive drums. Each of the plurality of light source emits a laser beam. The deflector is provided in the casing for deflecting the laser beam. The optical system is provided in the casing for guiding the deflected laser beam to a corresponding one of the plurality of photosensitive drums to make the laser beam scan the corresponding one of the plurality of photosensitive drums. The storage device stores a characteristic related to the laser beam scanning the corresponding one of the photosensitive drums.