A semiconductor light emitting device includes a first conductivity-type first semiconductor layer, a second conductivity-type second semiconductor layer, a semiconductor light emitting layer, and first and second electrodes. The semiconductor light emitting layer is provided between the first semiconductor layer and the second semiconductor layer, and includes a multiple quantum well structure. The quantum well structure includes well layers and barrier layers each laminated alternately, each of the well layers being not less than 6 nm and not more than 10 nm. The first and second electrodes are electrically connected to the first and second semiconductor layers such that current flows in a direction substantially vertical to the main surface.