A light emitting device includes an optical fiber plug formed with a through-hole into which a bundle of optical fibers is inserted and a light-emitting device holder formed with a through-hole in which a condenser lens and a light emitting device are accommodated, and the optical fiber plug is assembled with the light-emitting device holder so that the light emitting device is optically coupled to the optical fiber through the condenser lens; a positioning device, a hyperboloid lens surface or a reflecting surface is formed in the optical fiber plug/light emitting device holder, condenser lens or the inner surface of the light-emitting device holder so that the light incident on the light input end is increased by virtue of the exact positioning between the optical fiber and optical axis, reduction of aberration or increase of light directed to the condenser lens.