A light source device according to the present disclosure includes a light source section, a first light separation element for transmitting a part of first light entering the first light separation element irrespective of a polarization component, and reflecting another part of the first light irrespective of a polarization component, a second light separation element for reflecting a part of the first light entering the second light separation element, a diffusion element for diffusing and emitting another part of the first light entering the diffusion element, and a wavelength conversion element for performing wavelength conversion on a part of the first light entering the wavelength conversion element to emit second light, wherein the second light separation element transmits a first polarization component with respect to the second light, and reflects a second polarization component.