To execute such automatic adjustment operation that the irregularity of a scanning cycle is not caused by detecting the position of the main scanning and the sub-scanning directions of a light beam from a laser array and adjusting an interval between the light beams in the sub-scanning direction by controlling the rotation of the laser array, based on the detected information.

A light source unit 1 is constituted of the laser array obtained by arranging a plurality of semiconductor lasers in a line so that a plurality of lines are scanned in parallel in the sub-scanning direction with a plurality of laser beams internally modulated according to image data and simultaneously recorded. Besides, it is provided with an index sensor 6 detecting the position of the main scanning and the sub-scanning directions of the light beam from the laser array in an optical path and a means rotating the laser array. Then, the rotation of the laser array is controlled based on the detected information so as to adjust the interval between the laser beams in the sub-scanning direction. Thus, the irregularity of the scanning cycle easily caused when the plural lasers are simultaneously operated is eliminated and a high-speed laser recording action without scanning irregularity is realized.