A power supply system (10) is provided with a power supply device (100) for supplying a load device (200) with power; an electrical storage device (300) for supplying the load device (200) with power by replacing the power supply device (100) when the power supply device (100) is stopped; and a power supply control device (500) which controls power supply from the electrical storage device (300) to the load device (200) by monitoring the status of the electrical storage device (300) and detecting an abnormal status of the electrical storage device (300). The power supply control device (500) shortens a monitoring cycle for monitoring the status of the electrical storage device (300) when disaster information, from which stopping of the power supply device (100) can be predicted, is acquired, and surely monitors the status of the electrical storage device (300) when the power supply device (100) is stopped. Therefore, a backup function is continuously operated as long as possible.