According to one embodiment, a semiconductor light emitting device includes an n-type first semiconductor layer, a p-type second semiconductor layer and a light emitting layer. The light emitting layer is provided between the first and second semiconductor layers, and includes a plurality of barrier layers including a nitride semiconductor and a well layer provided between the barrier layers and including a nitride semiconductor containing In. The barrier layers and the well layer are stacked in a first direction from the second semiconductor layer toward the first semiconductor layer. The well layer has a p-side interface part and an n-side interface part. Each of the p-side and the n-side interface part include an interface with one of the barrier layers. A variation in a concentration of In in a surface perpendicular to the first direction of the p-side interface part is not more than that of the n-side interface part.