An insulated light-reflective substrate, comprising a substrate and an anodized film provided on the surface of the substrate, wherein: the substrate has at its surface an aluminum alloy layer of a thickness of not less than 10 µm; the aluminum alloy layer has an aluminum purity of 99.9% by weight or higher, with the total content of Si and Fe in the layer being not more than 0.005% by weight, and the content of inevitable impurities in the layer as components other than Al, Si, Fe, Ga and Zn being not more than 0.01% by weight; the anodized film has micropores each extending from the surface of the film in the direction of thickness; and the ratio of center line length to depth of the micropores is 1.0 to 1.2.