A III group nitride system compound semiconductor light emitting element has: a transparent substrate that is of a material except for III group nitride system compound semiconductor; a convex light trapping member that is formed directly or through a buffer layer on the surface of the transparent substrate; and a III group nitride system compound semiconductor layer that is formed on the surface of the transparent substrate. The light trapping member has a refractive index substantially equal to that of the transparent substrate or closer to that of the transparent substrate than that of the III group nitride system compound semiconductor layer.