A nanostructure semiconductor light emitting device may include: a base layer formed of a first conductivity-type semiconductor material; an insulating layer disposed on the base layer and having a plurality of openings exposing portions of the base layer; a plurality of nanocores disposed on the exposed portions of the base layer and formed of a first conductivity-type semiconductor material, each of which including a tip portion having a crystal plane different from that of a side surface thereof; a first high resistance layer disposed on the tip portion of the nanocore and formed of an oxide containing an element which is the same as at least one of elements constituting the nanocore; an active layer disposed on the first high resistance layer and the side surface of the nanocore; and a second conductivity-type semiconductor layer disposed on the active layer.