There is provided a nanostructure semiconductor light emitting device including: a base layer formed of a first conductivity-type nitride semiconductor; and a plurality of light emitting nanostructures disposed to be spaced apart from one another on the base layer, wherein each of the plurality of light emitting nanostructures includes a nanocore formed of a first conductivity-type nitride semiconductor; a stress control layer disposed on a surface of the nanocore and including a nitride semiconductor containing indium; an active layer disposed on the stress control layer; a second conductivity-type nitride semiconductor layer disposed on the active layer; and a defect blocking layer disposed on at least a portion of the stress control layer and including a nitride semiconductor layer having a lattice constant lower than that of the stress control layer.