There is provided a semiconductor light emitting device including: first and second conductivity type semiconductor layers; and an active layer disposed between the first and second conductivity type semiconductor layers and having a structure in which a plurality of quantum barrier layers and a plurality of quantum well layers are alternately disposed, wherein at least one of the plurality of quantum well layers includes a first region in which band gap energy is reduced through a first slope and a second region in which band gap energy is reduced through a second slope different from the first slope. The influence of polarization is minimized by adjusting the shape of the band gap of the quantum well layer, crystallinity and internal quantum efficiency can be enhanced.