A lamp driving circuit includes a first printed circuit board and a second printed circuit board. The first printed circuit board includes a switching unit for switching an input power source, a control unit for controlling the switching unit, an inverter transformer connected to the switching unit, and a voltage conversion unit for converting a feedback reference current for controlling an output current applied from the inverter transformer into a reference voltage and applying the reference voltage to the control unit. The voltage conversion unit is connected to the inverter transformer and the control unit. The voltage conversion unit is connected to a first feedback terminal. The second printed circuit board includes a plurality of balance coils connected to a plurality of lamps so that the same output currents are applied to the lamps, a second feedback terminal connected to the first feedback terminal, and a current conversion unit connected to the second feedback terminal.