An optical module that installs a plurality of laser diodes (LDs) and a composite prism to condense optical beams emitted from the LDs is disclosed. The LDs are arranged on a line so as to level the optical beams within a plane. The composite prism includes input surfaces and output surfaces each corresponding to respective one of the input surfaces. The composite prism outputs optical beams whose intervals are narrowed compared with intervals of the optical beams entering therein.