A semiconductor light emitting device includes: a light emitting structure including a first conductive type semiconductor layer, a second conductive type semiconductor layer and an active layer between the first conductive type semiconductor layer and the second conductive type semiconductor layer; and a first electrode on the first conductive type semiconductor layer, wherein the light emitting structure includes an outer groove formed at an outer area of the light emitting structure, wherein a thickness of an outmost area of the light emitting structure is smaller than a thickness of an center area of the light emitting structure, and wherein the first conductive type semiconductor layer includes AlGaN layer and the second conductive type semiconductor layer includes AlGaN layer.