A driving device of a light source for a display device is provided. The light source includes a plurality of lamps connected in parallel to each other and each lamp has a first terminal and a second terminal. The driving device also includes a lamp state sensing unit sensing driving voltages applied to the respective lamps, comparing the sensed driving voltages to a reference voltage, and outputting a lamp state sensing signal having an information informing an over-current state for at least one lamp; and an inverter turning the lamps on or off by applying an AC voltage to the lamps and controlling the AC voltage based on the lamp state sensing signal. The reference voltage is varied depending on the magnitude of the driving voltages applied to the respective lamps.