A porcelain enamel substrate mounts a light emitting device in which a porcelain enamel layer is coated onto a surface of a core metal, and a reflective cup portion that has a flat bottom surface and a sloping portion that surrounds this bottom surface is provided on a light emitting device mounting surface, and an electrode for energizing a light emitting device is provided on the light emitting device mounting surface, and the thickness of the electrode within the reflective cup portion is within a range of 5 .mu.m to 100 .mu.m.