A DC power supply system that limits the number of times of charging/discharging of the storage battery when a DC load is connected to a DC bus line. The system includes a DC bus line connectable to a DC load; a power generation device for supplying electric power to the DC bus line; a secondary battery for supplying electric power to the DC bus line; a DC-AC converter connected between the DC bus line and an AC power system; and a controller that controls power supply from the power generation device, the secondary battery, and the DC-AC converter to the DC bus line, and when the power supply of the power generation device cannot satisfy a power supply request of the DC load, the controller controls the DC-AC converter to supply electric power in preference to the secondary battery from the power system.