Provided are a light emitting device, a method of manufacturing the light emitting device, a light emitting device package, and a lighting system. The light emitting device includes a reflective layer including a first GaN-based semiconductor layer having a first refractive index, a second GaN-based semiconductor layer having a second refractive index less than the first refractive index, and a third GaN-based semiconductor layer having a third refractive index less than the second refractive index and a light emitting structure layer including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer on the reflective layer.