A nitride semiconductor structure including a substrate, a first type nitride semiconductor layer disposed on the substrate, an active layer disposed between the substrate and the first type nitride semiconductor layer and a second type nitride semiconductor layer disposed between the substrate and the active layer is provided. The active layer includes a first multiple quantum well structure including a plurality of first quantum well layers and a plurality of first barrier layers staggered with each other, and a second multiple quantum well structure including a plurality of second quantum well layers and a plurality of second barrier layers staggered with each other. A second type dopant is doped into at least one of the second barrier layers, and a concentration of the second dopant in the second barrier layer is higher than that of the second dopant in the second type nitride semiconductor layer.