An LED backlight device includes a first substrate having optical transparency and having first and second surfaces. An LED thin-film layered structure is fixed to the first surface of the first substrate, and is formed of epitaxially grown inorganic material layers as a P-N junction device. An anode electrode of the LED thin-film layered structure is connected to an anode driver IC via an anode wiring. A cathode electrode of the LED thin-film layered structure is connected to a cathode driver IC via a cathode wiring. A phosphor is provided on the second surface of the first substrate. The LED backlight device further includes a second substrate having optical transparency and having first and second surfaces. The first surface of the second substrate faces the first surface of the first substrate. A reflection layer is provided on the second surface of the second substrate.