Disclosed herein is a charging system using a wound rotor synchronous motor, capable of increasing a battery charging capacity while reducing the volume, weight, and/or cost of a vehicle increased dueto an on-vehicle charging circuit. The charging system includes an inverter converting a DC output of a battery into a plurality of AC signals having different phases, a wound rotor synchronous motorhaving a plurality of stator coils, to which the AC signals having different phases are respectively input, and a field coil forming a mutual inductance with the stator coils, the field coil being installed in a rotor to form a magnetic flux using the DC output of the battery, and a controller allowing the battery and the field coil to be insulated from each other in a charge mode in which electricity from a grid is applied to the field coil of the wound rotor synchronous motor.