The present invention relates to an apparatus for supplying power source for providing power source to a plurality of display devices. The apparatus for supplying power source includes a boosting circuit and a voltage adjusting circuit. The boosting circuit boosts a battery voltage to a first voltage, and supplies the first voltage to a first display device. The voltage adjusting circuit adjusts the first voltage to a second voltage, and supplies the second voltage to a second display device. The apparatus supplies a voltage outputted from a boosting circuit to a first display device, downs the voltage through a voltage adjusting circuit, and then supplies the downed voltage to a second display device. In other words, the apparatus of the present invention may provide voltages having different magnitude to a plurality of display devices, respectively.