There is provided a nitride semiconductor light emitting device having a light reflection layer capable of preventing reflectivity from lowering and luminance from lowering due to deterioration of quality of an active layer. A nitride semiconductor laser includes at least a light emitting layer forming portion (3) provided on a first light reflection layer (2) provided on a substrate (1). The first light reflection layer (2) is formed with laminating a low refractivity layer (21) and a high refractivity layer (22) which have a different refractivity from each other, and the low refractivity layer (21) of the first light reflection layer is formed with a single layer structure of an AlxGa1−xN layer (0≦x≦1), and the high refractivity layer (22) of the first light reflection layer is formed with a multi layer structure formed by laminating alternately an AlyGa1−yN layer (0≦y≦0.5 and y