The object is to decrease the size of an entire backlight device including an inverter circuit board and the cost for producing the backlight device. The backlight device includes a lamp (20a), an inverter circuit that generates a drive voltage for driving the lamp (20a) from an inputted voltage, a socket section (26a) that holds an end part of the lamp (20a) and applies the drive voltage to an electrode lead (28a) led out from the end part of the lamp (20a), and a metal chassis (31). The socket section (26a) has a dielectric (dielectric unit 32) between a flat part of the electrode lead (28a) of the lamp (20a) and the metal chassis (31). The electrode lead (28a), the dielectric (dielectric unit 32) and the metal chassis (31) function as a resonant capacitor of an output transformer of the inverter circuit.