The periphery of a fluorescent body is reliably sealed, and entry of moisture or volatilized gas is prevented. An illumination optical unit includes an optical fiber, a fluorescent body, a ferrule as a holding member holding the fluorescent body and the optical fiber, a tubular sleeve member that covers the outer periphery of the fluorescent body, and a protective cover. The ferrule holds the fluorescent body and is fitted into a fitting hole of the sleeve member. An inner peripheral face of the sleeve member and an outer peripheral face of the protective cover are bonded together to seal the distal end side of the fluorescent body, and the fitting hole of the sleeve member and an outer peripheral face of the ferrule are bonded together to bond the proximal end side of the fluorescent body.