A back lighting unit is disclosed in which lower and upper surfaces of a light transmitting plate function as incident and exit surfaces of light, respectively, and a phosphor film structure for wavelength-converting the light is provided at a position which the light is incident on or exits from. The disclosed back lighting unit includes a light emitting means including a light emitting diode disposed to emit light upwards; a light transmitting plate disposed over the light emitting diode, the light transmitting plate having a lower surface allowing light to be incident thereon and an upper surface allowing light to exit therefrom; and a phosphor film structure including a particulate phosphor and formed on at least one of the lower and upper surfaces of the light transmitting plate.