A light emission device and a display device using the light emission device as a light source are provided. The light emission device includes first and second substrates facing each other, an electron emission unit located on an inner surface of the first substrate, a phosphor layer located on an inner surface of the second substrate and adapted to be excited by electrons emitted from the electron emission unit, an anode electrode located on the phosphor layer, a heat dissipation plate located at a side of the first substrate, and a thermal diffuser plate located on the second substrate and thermally coupled to the heat dissipation plate. The thermal diffuser plate is configured to transmit light emitted by the phosphor layer.