Abstract: A plurality of light emitting units are prepared each of which is provided with a laser diode having a laser diode chip which emits one beam and a collimator lens for converting a beam emitted from the laser diode into a parallel beam. The light emitting units are fixed to a bar body so as to be in a row. A plurality of such bar bodies are prepared, and by fixing the bar bodies to a substrate, the light source units are arranged in a matrix form. The positions of the light emitting units are adjusted and fixed after the light emitting units are fitted in the bar bodies so that a plurality of beams emitted from the laser diodes are in parallel with one another at predetermined intervals.