A nitride-based semiconductor light-emitting device having enhanced efficiency of carrier injection to a well layer is provided. The nitride-based semiconductor light-emitting device comprises a hexagonal gallium nitride-based semiconductor substrate 5, an n-type gallium nitride-based semiconductor region 7 disposed on the principal surface S1 of the substrate 5, a light-emitting layer 11 having a single-quantum-well structure disposed on the n-type gallium nitride-based semiconductor region 7, and a p-type gallium nitride-based semiconductor region 19 disposed on the light-emitting layer 11. The light-emitting layer 11 is disposed between the n-type gallium nitride-based semiconductor region 7 and the p-type gallium nitride-based semiconductor region 19. The light-emitting layer 11 includes a well layer 15 and barrier layers 13 and 17. The well layer 15 comprises InGaN. The principal surface S1 extends along a reference plane S5 tilting from a plane perpendicular to the c-axis of the hexagonal gallium nitride-based semiconductor at a tilt angle in a range of not less than 63 degrees and not more than 80 degrees or in a range of not less than 100 degrees and not more than 117 degrees.