A light source device includes a light source, a plurality of wavelength conversion units, and a plurality of optical systems. The plurality of wavelength conversion units each includes a wavelength conversion region configured to receive light emitted from the light source and emit light with a wavelength different from a wavelength of the received light. The plurality of optical systems are configured to form images of wavelength conversion regions of the plurality of wavelength conversion units. The light source is configured to irradiate the wavelength conversion units with light at a same timing. The plurality of optical systems are configured to cause the images of the wavelength conversion regions of the plurality of wavelength conversion units to be adjacent to or superimposed on each other.