There is provided a nitride semiconductor device. A nitride semiconductor device according to an aspect of the invention may include: an n-type nitride semiconductor layer; a p-type nitride semiconductor layer; an active layer provided between the n-type and p-type nitride semiconductor layers and having quantum well layers and quantum barrier layers alternately stacked on each other; and an electron blocking layer provided between the active layer and the p-type nitride semiconductor layer, and having a plurality of first nitride layers formed of a material having a higher band gap energy than the quantum barrier layers and a plurality of second nitride layers formed of a material having a lower band gap energy than the first nitride layers, the first and second nitride layers alternately stacked on each other to form a stacked structure, wherein the plurality of first nitride layers have energy levels bent at predetermined inclinations, and with greater proximity to the p-type nitride semiconductor layer, the first nitride layers have a smaller inclination of the energy level.