A semiconductor light emitting device includes an Si substrate having opposed front and rear surfaces; an amorphous or polycrystalline first buffer layer disposed on the front surface of the Si substrate; and GaN series compound semiconductor layers successively disposed on the first buffer layer and including a light emitting region where light is produced by recombination of electrons and holes. In this light emitting device, since the Si substrate is cleavable, it is possible to produce resonator facets by cleaving. In addition, since the Si substrate is electrically conductive, a structure in which a pair of electrodes are respectively located on opposed upper and lower surfaces of the light emitting device is realized. Further, since the Si substrate is inexpensive, the light emitting device is obtained at low cost. Furthermore, since the amorphous or polycrystalline first buffer layer is disposed on the Si substrate, in the initial state of the growth of the GaN series compound semiconductor layers, plenty of growth nuclei are created, and the growth nuclei promote two-dimensional growth. As a result, high-quality GaN series compound semiconductor layers are obtained.