Disclosed is a semiconductor light emitting device comprising: a substrate; a first semiconductor layer, which is provided on the substrate and has a first conductivity; an active layer, which is provided on the first semiconductor layer and generates ultraviolet light by electron-hole recombination; a second semiconductor layer, which is provided on the active layer and has a second conductivity different from the first conductivity; a first electrode electrically connected to the first semiconductor layer; a second electrode electrically connected to the second semiconductor layer; a second region that includes a plurality of protruded parts of the active layer and the second semiconductor layer protruded from the first semiconductor layer as seen in cross-sectional view and recesses between the protruded parts; and a first region surrounding the second region.