The light emitting unit of this invention mainly comprises: a lamp holder made of insulating ceramics with high thermal conductivity; a plurality of heat dissipating fins protruding integrally from the outer end face of the lamp holder; a light-transmissive lamp tube provided on the lamp holder; a light source mounted in the light-transmissive lamp tube; a lampshade having a light reflecting surface in the inner edge being provided on the lamp holder corresponding to the light-transmissive lamp tube; and a light-transmitting element, corresponding to the transmissive lamp tube, provided outside the lampshade. According to this structure, significant illumination effect can be obtained from the entire light emitting device. Moreover, good heat dissipation effect can also be achieved by the lamp holder made of insulating ceramics with high thermal conductivity and the heat dissipating fins formed integrally with the lamp holder, such that the reduced service life, light depreciation and burn-out of the inside light source caused by overheating of the light source can be avoided so as to increase the entire performance in use.