A hybrid drive system includes first and second power supply devices (11 and 21) supplying direct-current power, first and second power storage devices (13 and 23) respectively connected to the first and second power supply devices and accumulating or discharging direct-current power, a first load device 12 receiving direct-current power from the first power supply device and the first power storage device and driving a first load, a second load device 22 receiving direct-current power from the second power supply device and the second power storage device and driving a second load, a first diode 31a including an anode side terminal connected to an output side of the first power storage device, a second diode 31b including an anode side terminal connected to an output side of the second power storage device, and an auxiliary power supply device to which a connection terminal of cathode side terminals of the first and second diodes is connected as an input terminal.
