To suppress the occurrence of luminance irregularity at a low cost, in a direct type backlight device.

This backlight device includes one luminance sensor 32 for every two or more lamps 10. The luminance sensor 32 detects an average value K of luminance of light emitted from the lamps 10 in each backlight box 11. A lamp control circuit 201 outputs a control signal P, based on the average value K of the luminance. A lamp driving circuit 202 applies a voltage V1 between both ends of a primary coil 211 of a transformer 21, based on the control signal P. The lamps 10 emit light based on a voltage V2 generated between both ends of the secondary coil 212 of the transformer 21 in response to the voltage V1. Control loops for controlling the luminance of the lamps 10 are formed to the same number as that of the backlight boxes 11.