A nitride semiconductor device includes an active layer formed between an n-type cladding layer and a p-type cladding layer, and a current confining layer having a conductive area through which a current flows to the active layer. The current confining layer includes a first semiconductor layer, a second semiconductor layer and a third semiconductor layer. The second semiconductor layer is formed on and in contact with the first semiconductor layer and has a smaller lattice constant than that of the first semiconductor layer. The third semiconductor layer is formed on and in contact with the second semiconductor layer and has a lattice constant that is smaller than that of the first semiconductor layer and larger than that of the second semiconductor layer.