The Group III nitride semiconductor light-emitting device has an insulating multilayer film intervening between a second semiconductor layer and a transparent electrode. The insulating multilayer film serves as a distributed Bragg reflector and is formed in a region including a projection area obtained by projecting a p-electrode to the p-type contact layer. The insulating multilayer film has a first region and a second region, wherein the first region has a layer thickness greater than 95% of the maximum film thickness of the insulating multilayer film, and the second region has a layer thickness not greater than 95% of the maximum film thickness of the insulating multilayer film. The second surface of the insulating multilayer film in the second region has a slope having a dent portion denting toward the first surface of the insulating film.