PURPOSE: To correct the sensitivity characteristic deviation of a photosensitive body and to obtain a recording image of high quality reduced at its fogging or density difference by controlling the exposing time of each part on the photosensitive body in synchronism with the generating period of the sensitivity characteristic deviation.

CONSTITUTION: A waveform generator WG1 for correcting the distribution of the photosensitive characteristic deviation of the photosensitive body generates a prescribed waveform signal in synchronism with a clock ' synchronized with a polygon mirror 9 or the main scanning of a laser beam and superposes the generates signal to an input image signal to send the superposed signal to a comparator 3. A waveform generator WG2 generates a triangular wave or the like in synchronism with an image clock and sends the wave to the comparator 3. As the result of comparison, the light emitting time of a semiconductor laser 5 to each picture element is shorter than the whole lighting time on the front side of the photosensitive body 6 with high sensitivity and that is equal to the whole lighting time on the depth side of the photosensitive body 6 with low sensitivity. A laser driver 4 is driven by a laser lighting signal corrected by said procedure and the semiconductor laser 5 is flickered.