A semiconductor light emitting device is provided, in which the light emitting efficiency of a LED is improved. A semiconductor light emitting device (11) includes a light emitting layer (16) made of a GaN-based semiconductor sandwiched with an n-type GaN-based semiconductor layer (17) and a p-type GaN-based semiconductor layer (15), and a ZnO-based or an ITO transparent electrode layer (14). Further, a value of an equation represented by 3t/(A/π)1/2−3(t/(A/π)1/2)2+(t/(A/π)1/2)3 is 0.1 or more, where a thickness of the transparent electrode layer is represented by t and an area of the light emitting layer (light emitting area) of the light emitting device (11) is represented by A. The light emitting efficiency is improved using the transparent electrode layer (14) having an optimum thickness to the light emitting area.