An LCD device and a driving method thereof are provided. The LCD device includes a plurality of data driver ICs, a timing controller, a reference voltage generator, and a PCB. The data driver ICs include a gamma voltage generator which generates a gamma voltage. The timing controller generates an EPI packet for controlling the data driver ICs. The reference voltage generator reduces the driving voltage, and supplies the reduced driving voltage to the data driver IC. The reference voltage generator, the data driver ICs, and the timing controller are mounted on the PCB. A first transmission line which connects the reference voltage generator and the data driver ICs, and a second transmission line which connects the timing controller and the data driver ICs are formed on the PCB.