In a multiple power supply apparatus installed in a vehicle, a first power supply system includes a generator and a first battery. The generator is driven by an operation of the engine. The first battery is chargeable by an electrical output of the generator. A second power supply system includes a second battery. The second battery works to supply electrical power to an electrical load installed in the vehicle. A power transfer module is operative to transfer electrical power supplied from the first power supply system based on at least one of the electrical output of the generator and a charged level of the first battery to the second power supply system. The power transfer module is integrally joined to the first battery to constitute a battery module.