A GaN-based semiconductor light-emitting element includes a first GaN-based compound semiconductor layer of n-conductivity type, an active layer, a second GaN-based compound semiconductor layer of p-conductivity type, a first electrode electrically connected to the first GaN-based compound semiconductor layer, a second electrode electrically connected to the second GaN-based compound semiconductor layer, an impurity diffusion-preventing layer composed of an undoped GaN-based compound semiconductor, the impurity diffusion-preventing layer preventing a p-type impurity from diffusing into the active layer, and a laminated structure or a third GaN-based compound semiconductor layer of p-conductivity type. The impurity diffusion-preventing layer and the laminated structure or the third GaN-based compound semiconductor layer of p-conductivity type are disposed, between the active layer and the second GaN-based compound semiconductor layer, in that order from the active layer side.