A light source device includes a first light source, a fluorescent material, a second light source, and a synthesis member. The synthesis member includes a visible light reflecting film, and a transmitting window which is disposed in the visible light reflecting film to transmit the visible light. The second light source, the fluorescent material and the synthesis member are mutually arranged in such positional relations that the transmitting window is positioned along optical axis of light emitted from the second light source and that generated light emitted from the fluorescent material is reflected in an optical axis direction of the light emitted from the second light source by the visible light reflecting film.