Each light source has plural light emitting portions that are arranged at the different positions in at least a sub-scanning corresponding direction. A memory of a scanning control device stores correction data of the deviation of the beam pitch, correction data of the light amount difference, and correction data to decrease an influence of a reciprocity failure, for each combination of pixel forming light emitting portions. When a write signal is generated, a write control circuit of the scanning control device reads the correction data of the deviation of the beam pitch, the correction data of the light amount difference, and the correction data of the reciprocity failure according to the combination of the pixel forming light emitting portions from the memory, overlaps the read correction data to correction data of an APC, and outputs the overlapped data to a corresponding light source unit as light amount correction data.