There is provided a nanostructure semiconductor light emitting device may including: a base layer formed of a first conductivity-type semiconductor, an insulating layer formed on an upper surface of the base layer and including a first region having a plurality of openings and a plurality of second regions positioned in the plurality of openings and spaced apart from the first region, dielectric nanocores disposed in the plurality of second regions, and a plurality of light emitting nanostructures each including a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer sequentially disposed on the dielectric nanocores.