Semiconductor lasers are arranged in a plurality of columns. The columns of the respective semiconductor lasers include semiconductor laser installed columns. Reflecting mirrors in the respective semiconductor laser installed columns reflect light in substantially the same axial direction as viewed from above, and constitute beam groups. The beam groups of the respective semiconductor laser installed columns are formed on both sides in a width direction of a housing. That is, the beam groups are configured for each of the semiconductor laser installed columns, and the respective beam groups are formed on mutually different axes as viewed from above.