A method of fabricating a semiconductor light emitting device includes forming a first conductivity type semiconductor layer, forming an active layer by alternately forming a plurality of quantum well layers and a plurality of quantum barrier layers on the first conductivity type semiconductor layer, and forming a second conductivity type semiconductor layer on the active layer. The plurality of quantum barrier layers include at least one first quantum barrier layer adjacent to the first conductivity type semiconductor layer and at least one second quantum barrier layer adjacent to the second conductivity type semiconductor layer. The forming of the active layer includes allowing the at least one first quantum barrier layer to be grown at a first temperature and allowing the at least one second quantum barrier layer to be grown at a second temperature lower than the first temperature.