A power supply system includes: a hydrogen generation device that uses electric power to generate hydrogen; a hydrogen storage device that stores hydrogen generated by the hydrogen generation device; a fuel cell system that uses hydrogen stored in the hydrogen storage device to generate electric power; a power storage device; and a control device executing at least one of first control and second control based on an electricity expense, the first control controlling a first ratio between electric power to be supplied from a natural energy power generation device to the hydrogen generation device and electric power to be supplied from the natural energy power generation device to the power storage device, the second control controlling a second ratio between electric power to be supplied from the power storage device to a load and electric power to be supplied from the fuel cell system to the load.