A power supply system control device for controlling a power supply system including an electric generator, a first electricity storage configured to be charged with and to discharge electric power generated by the electric generator, a second electricity storage configured to be charged with and to discharge the generated electric power, two paths connecting between the first electricity storage and the second electricity storage, a switching unit including a first switch configured to switch between a conductive state and a non-conductive state of one of the paths, and a second switch configured to switch between a conductive state and a non-conductive state of the other of the paths, and an electric load of a vehicle that is connected to the first electricity storage side of the switching unit.