A submount for a light emitting diode and its manufacturing method, the submount including a reflector and having a compact size. The submount for the light emitting diode comprises a Si base substrate having input/output terminals formed on a front side thereof, and a Si reflector having a sloped through hole and a reflecting film formed at least on a slope defining the through hole. The Si reflector is mounted on the Si base substrate and is fixedly joined to the Si base substrate. The Si reflector and the Si base substrate are joined to each other by a thin film solder.