An object is to prevent a mistaken shutoff caused by the mistaken registration of an appliance of which an amount of gas used changes. An individual flow registration maintenance unit maintains a registered flow rate deleted due to an increase/decrease in flow rate, again, performs determination on the flow rate maintained when a new flow rate is registered or a flow rate added with the maintained flow rate, and in the case where it is regarded to be the same, re-register the maintained flow rate.