There is provided a nitride semiconductor device including an active layer of a superlattice structure. The nitride semiconductor device including: a p-type nitride semiconductor layer; an n-type nitride semiconductor layer; and an active layer disposed between the p-type and n-type nitride layers, the active layer comprising a plurality of quantum barrier layers and quantum well layers deposited alternately on each other, wherein the active layer has a superlattice structure where the quantum barrier layer has a thickness for enabling a carrier injected from the p-type and n-type nitride semiconductor layers to be tunneled therethrough, and at least one of the quantum barrier layers has an energy band gap greater than another quantum barrier layer adjacent to the n-type nitride semiconductor layer.