Abstract: A nitride semiconductor structure and a semiconductor light emitting device including the same are revealed. The nitride semiconductor structure includes a multiple quantum well structure formed by a plurality of well layers and barrier layers stacked alternately. One well layer is disposed between every two barrier layers. The barrier layer is made of AlxInyGa1-x-yN (0<x<1, 0<y<1, 0<x+y<1) while the well layer is made of InzGa1-zN (0<z<1). Thereby quaternary composition is adjusted for lattice match between the barrier layers and the well layers. Thus crystal defect caused by lattice mismatch is improved.