A semiconductor light emitting device includes: a light emitting diode unit including a light-transmissive substrate having a face sloped upwardly at a lower edge thereof. A rear reflective lamination body is formed on the lower face and the surrounding sloped face of the light-transmissive substrate. The rear reflective lamination body includes an optical auxiliary layer and a metal reflective film formed on a lower face of the optical auxiliary layer. A junction lamination body is provided to a lower face of the rear reflective lamination body. The junction lamination body including a junction metal layer made of a eutectic metal material and a diffusion barrier film.