A nanostructure semiconductor light emitting device may include a base layer having first and second regions and formed of a first conductivity-type semiconductor material; a plurality of light emitting nanostructures disposed on the base layer, each of which including a nanocore formed of a first conductivity-type semiconductor material, and an active layer and a second conductivity-type semiconductor layer sequentially disposed on the nanocore; a contact electrode disposed on the light emitting nanostructures to be connected to the second conductivity-type semiconductor layer; a first electrode connected to the base layer; and a second electrode covering a portion of the contact electrode disposed on at least one of light emitting nanostructures disposed in the second region among the plurality of light emitting nanostructures, wherein light emitting nanostructures disposed in the second region and light emitting nanostructures disposed in the first region among the plurality of light emitting nanostructures have different shapes.