A scanning optical device for scanning a material to be scanned with beams emitted from a light source (1) thereof, has a storage device for storing information relating to the quantity of deviation of a scanning optical system. The convergent position of the beams is adjustable in the direction of the optical axis by at least partially controlling the elements of the scanning optical system in accordance with information relating the quantity of deviation supplied by the storage device. The quantity of deviation such as an image distortion of the scanning optical system can be compensated by a simple structure. Therefore, a recording device or reading device employing the scanning optical system exhibiting high resolution, low cost and a capability of preventing deterioration in the gradation expression can be realized.