The present invention relates to an apparatus for supplying power source for providing certain voltage to a first display device and a second display device. The apparatus for supplying power source includes a boosting circuit, a boosted voltage detecting circuit and an output selecting circuit. The boosting circuit boosts a battery voltage. The boosted voltage detecting circuit detects the boosted battery voltage, and transmits the detection result to the boosting circuit. The output selecting circuit is coupled to the boosting circuit and the boosted voltage detecting circuit, and provides selectively the boosted battery voltage to a first display device and a second display device. The apparatus provides certain voltage to a first display device and/or a second display device, and thus the size of a dual panel apparatus employing the display devices may be reduced.