In a nitride semiconductor light-emitting device (11), an emission region (17) has a quantum well structure (19), and lies between an n-type gallium nitride semiconductor region (13) and a p-type gallium nitride semiconductor region (15). The quantum well structure (19) includes a plurality of first well layers (21) composed of InxGa1-xN, one or a plurality of second well layers (23) composed of InyGa1-yN, and barrier layers (25). The first and second well layers (21) and (23) are arranged in alternation with the barrier layers (25). The second well layers (23) lie between the first well layers (21) and the p-type gallium nitride semiconductor region (15). The indium component y of the second well layers (23) is smaller than indium component x of the first well layers (21), and the thickness DW2 of the second well layers (23) is greater than the thickness DW1 of the first well layers (21).