A light source apparatus includes a short-arc-type mercury lamp, a main reflection mirror, a sub-reflection mirror, and an optical element. The sub-reflection mirror surrounds an opening of the ellipsoid main reflection mirror. The sub-reflection mirror reflects a portion of the light emitted from the lamp toward the main reflection mirror. The light reflected by the sub-reflection mirror is reflected toward the main reflection mirror. The optical element is arranged between a second focal point of the main reflection mirror and the sub-reflection mirror. The light reflected by the main reflection mirror and passes through an opening of the sub-reflection mirror is incident upon an incidence-side face of the optical element. The optical element transmits visible light and to reflect ultraviolet light, while the main reflection mirror transmits infrared light and reflects ultraviolet light and visible light and the sub-reflection mirror reflects ultraviolet light and visible light.