According to one embodiment, a semiconductor light emitting device includes an n-type semiconductor layer, a p-type semiconductor layer, and a light emitting part. The n-type semiconductor layer includes a nitride semiconductor. The p-type semiconductor layer includes a nitride semiconductor. The light emitting part is provided between the n-type and the p-type semiconductor layers and includes an n-side barrier layer and a first light emitting layer. The first light emitting layer includes a first barrier layer, a first well layer, and a first AlGaN layer. The first barrier layer is provided between the n-side barrier layer and the p-type semiconductor layer. The first well layer contacts the n-side barrier layer between the n-side and the first barrier layer. The first AlGaN layer is provided between the first well layer and the first barrier layer. A peak wavelength λp of light emitted from the light emitting part is longer than 515 nanometers.