Backlight device, and liquid crystal display device using backlight device, and light-emitting diode used in same

A light-emitting diode is provided comprising: a light-emitting layer (14) which is provided on a transparent substrate (11) and emits light of a specific wavelength; a mirror layer (17) which is formed on the light-emitting side of the light-emitting layer (14) and has the function of reflecting light emitted from the light-emitting layer (14); and a reflection layer (18) which is provided on the substrate (11) side in such a way that the light-emitting layer (14) is positioned between the mirror layer (17) and the reflection layer (18). A diffusion layer which diffuses light emitted from the light-emitting layer (14) is positioned between the mirror layer (17) and the reflection layer (18).