To control each battery remaining amount in the power supply system of two systems independent from each other.

An electric power supply device has a plurality of systems. Each system has a battery for delivering/receiving electric power, a motor which has two or more independent windings each being changeable for output and regeneration and which outputs a drive torque in receiving power supply from the battery of self system or another system and generates electric power in performing regenerative control, and a drive circuit for controlling power transfer between the battery and the motor. One winding of the motor operates for output. In receiving electric power from the battery of one system and outputting the drive torque, the other winding operates for regeneration and generates electric power to charge the battery of the other system.