A method of manufacturing a semiconductor light emitting device includes stacking a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer on a substrate; forming a first electrode and a second electrode on the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, respectively; forming an insulating layer covering the first and second electrodes and having first and second openings partially exposing surfaces of the first and second electrodes, respectively; and performing a plasma treatment on a surface of the insulating layer and the partially exposed surfaces of the first and second electrodes to form an unevenness portion on the surface of the insulating layer and form an oxygen-depleted layer on the partially exposed surfaces of the first and second electrodes.