There is provided a light source unit including an excitation light source emitting excitation light, and a luminescent member having a transmission portion transmitting excitation light from the excitation light source, a first luminescent material layer placed beside the transmission portion on one side of the luminescent member and a second luminescent material layer placed beside the transmission portion on the other side of the luminescent member, wherein the first luminescent material layer and/or the second luminescent material layer emits luminous light by being excited by the excitation light, and wherein a guiding optical system is provided which shines excitation light which has passed through the transmission portion from the excitation light source on to the first luminescent material layer and causes luminous light emitted from the first luminescent material layer to be incident on the transmission portion.