The invention provides a highly reliable nitride semiconductor light emitting device improved in electrostatic discharge withstand voltage. In the light emitting device, an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer are sequentially formed on a substrate. The active layer features a multiple quantum well structure including a plurality of multiple quantum barrier layers and quantum well layers. At least one of the quantum barrier layers has a band-gap modulated multilayer structure.