A III V group nitride system semiconductor self-standing substrate has: a first III V group nitride system semiconductor crystal layer that has a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly; and a second III V group nitride system semiconductor crystal layer that is formed up to 10 .mu.m from the surface of the substrate on the first III V group nitride system semiconductor crystal layer and that has a dislocation density distribution that is substantially uniform.