The hydrogen gas supply device capable of detecting that the hydrogen gas storage volume of a tank has decreased to a predetermined value or less including a plurality of tanks each filled with a hydrogen storage alloy, an information obtaining device for obtaining information on the physical quantity of the plurality of tanks different from each other in hydrogen storage volume, and a signal outputting device for outputting information signal on the remaining amount of the hydrogen gas in the tanks by determining a hydrogen gas storage status of the plurality of tanks from information on the physical quantity, and detecting the decrease of the remaining amount of the hydrogen gas in all tanks in use to a predetermined value or less from the hydrogen gas storage status of the plurality of tanks.