A low temperature buffer layer made of GaN is formed on a sapphire substrate and an n type layer is formed thereon. An active layer is made of an InGaN based compound semiconductor. A GaN based compound semiconductor layer including an n-type layer, an active layer serving as a light emitting layer, and a p type layer are laminated on the sapphire substrate. A current diffusion film which is formed on the p-type layer for supplying the light emitting layer with a uniform current is formed of an electrically conductive metal having a high reflectance factor for light. The light emitting diode element is mounted on a circuit board so that the output light of the light emitting layer is emitted from the side of the sapphire substrate. Reflected light which is reflected on the current diffusion film is also emitted from the sapphire substrate.