A light source device includes a plurality of laser modules and a beam combiner. Each laser module includes a first laser diode configured to emit a first laser beam and a second laser diode configured to emit a second laser beam. The beam combiner has a first dichroic mirror region and a second dichroic mirror region. The first dichroic mirror region is configured to transmit the first laser beam going out from the first laser module, and to reflect the second laser beam going out from the second laser module. The second dichroic mirror region configured to transmit the second laser beam going out from the first laser module, and to reflect the first laser beam going out from the second laser module.