A light source device configured to emit a light beam in a first direction emits a first colored light beam from a first exit position, a second colored light beam longer in wavelength than the first colored light beam, a third colored light beam shorter in wavelength than the first colored light beam, and a fourth colored light beam, a mixed light beam including the first colored light beam and the second colored light beam enters an outgoing light switching device disposed in a light path of the fourth colored light beam.