In a backlight, for example, a pair of U-shaped discharge tubes are connected to connectors of a discharge tube lighting circuit. A secondary output voltage of a first transformer is applied to a first end of one U-shaped discharge tube via a power supply electrode. A secondary output voltage of a second transformer is applied to a first end of the other U-shaped discharge tube via a power supply electrode. A secondary output voltage of a third transformer is applied in common to the other (second) ends of the U-shaped discharge tubes via other power supply electrodes. The secondary output voltages of the first and second transformers are the same in polarity, and are opposite to the secondary output voltage of the third transformer in polarity.