A lamp driving device is provided for driving plural lamps. The lamp driving device includes a power conversion circuit and plural lamp connectors. The power conversion circuit is capable of converting an input voltage into a first DC voltage, and outputting a first current having a constant current value. The plural lamp connectors are serially connected with each other, and have respective positive terminals and respective negative terminals connected with corresponding lamps, thereby outputting respective output voltages and respective output currents to corresponding lamps. The first DC voltage is subject to voltage-division to obtain the output voltages, and the magnitudes of the output voltages from the lamps are substantially identical.