A reduction in utilization efficiency of laser beams emitted from laser emission portions of illumination means is limited and an exposure surface is exposed by beam spots with desired spot diameters and spot forms. At an exposure head, first microlenses are arranged in a two dimensional manner so as to correspond to micromirrors at a DMD, and apertures are arranged in a two dimensional manner at back side focusing positions of the first microlenses. With this exposure head, light source images, which are formed to be very small at back side focusing positions of the first microlenses by the first microlenses, are projected onto the exposure surface, and these light source images serve as beam spots BS and expose the exposure surface.