A nanostructure semiconductor light emitting device includes a base layer, an insulating layer, a plurality of light emitting nanostructures, and a contact electrode. The base layer is formed of a first conductivity-type semiconductor material. The insulating layer is disposed on the base layer. Each light emitting nanostructure is disposed in a respective opening of a plurality of openings in the base layer, and includes a nanocore formed of the first conductivity-type semiconductor material, and an active layer and a second conductivity-type semiconductor layer sequentially disposed on a surface of the nanocore. The contact electrode is spaced apart from the insulating layer and is disposed on a portion of the second conductivity-type semiconductor layer. A tip portion of the light emitting nanostructure has crystal planes different from those on side surfaces of the light emitting nanostructure.