A power supply system that supplies high-voltage power to a vehicle drive motor is provided to achieve reduction in size, weight and cost of power supply. The power supply system includes a plurality of battery modules connected in series. With the intermediate connection point of the battery modules as an electrical neutral point, power is supplied to a three-level inverter via a three-level-potential high-voltage power supply line having potentials of +150V and −150V relative to this neutral point. In the three-level inverter, direct-current electric power is converted into three-phase alternating-current electric power to drive an electric motor. Accordingly, the withstand-voltage performance required of control units or control elements connected to the high-voltage power supply line can be halved as compared with the related art, thereby allowing a reduction in the size, weight, and cost of the power supply system. Further, the electric power generated by a generator is converted into direct-current electric power by a three-level converter and supplied to the high-voltage power supply line to charge the battery modules.