A voltage setting value adjusting device includes a controller, a plurality of laser light sources and a voltage setting value adjusting circuit. The controller has a voltage setting value input end and a driving voltage output end. The laser light sources are coupled to the driving voltage output end, and the controller outputs a driving current to the laser light sources according to a voltage setting value. The voltage setting value adjusting circuit is coupled between the voltage setting value input end and the driving voltage output end to detect a driving voltage of the laser light sources and adjust the voltage setting value according to the driving voltage.