In an optical substrate (1), a concave-convex structure (12) including a plurality of independent convex portions (131 to 134) and concave portions (14) provided between the convex portions (131 to 134) is provided in a surface. The average interval Pave between the adjacent convex portions (131 to 134) in the concave-convex structure (12) satisfies 50 nm≦Pave≦1500 nm, and the convex portion (133) having a convex portion height hn satisfying 0.6 h≧hn≧0 h for the average convex portion height Have is present with a probability Z satisfying 1/10000≦Z≦1/5. When the optical substrate (1) is used in a semiconductor light-emitting element, dislocations in a semiconductor layer are dispersed to reduce the dislocation density, and thus internal quantum efficiency IQE is improved, and a waveguide mode is removed by light scattering and thus the light the extraction efficiency LEE is increased, with the result that the efficiency of light emission of the semiconductor light-emitting element is enhanced.