To aim at power saving of a liquid crystal display by changing over connection relations of high-frequency transformers in parallel connection, so as to attain a higher efficiency in the case luminance of a backlight is adjusted by brightness adjustment of the device to have consumption power changed.

In the backlight driving device equipped with a plurality of high-frequency transformers 102, 103 connected in parallel in an inverter power source circuit 10 and supplying power to the backlight 12 of the liquid crystal display through the high-frequency transformers, the high-frequency transformers 102, 103 are ones provided for outputting of a switching power source circuit, of which, primary sides are connected in parallel through a switch 105, which is alternatively turned off in accordance with a load factor of the switching power source circuit 101, and are connected in free adjustment as to the number of parallel connection.