It is an objective to appropriately assure a function of limiting use of appliances that cause changes in quantities of gas used. There are provided a flow detection unit 10; a flow computing unit 11; an average flow computing unit 12; a flow storage unit 13 that records an average flow quantity value; a flow change determination unit 14 that determines whether there is a flow change; a flow registration unit 15 that registers a flow quantity corresponding to a flow change or deletes a registered flow quantity close to the flow change when the flow change determination unit 14 has determined an incremental or decremental change; a flow memory unit 16; a flow change correction memory unit 17 that, when the flow change determination unit has determined presence of a change and when only the maximum flow quantity is registered, determines whether or not a sum of registered flow quantities deleted in the past and an average flow fall within a predetermined range; a determination period unit 18 that, when no flow change is determined to have been for a predetermined time period, deletes flow quantities in the flow memory unit and the registered flow quantity, thereby performing re-registration; a monitoring value memory unit 19; an abnormality determination unit 20 that compares the flow quantity value in the flow registration unit with a determination value of the monitoring value memory unit, thereby determining presence or absence of an abnormality; and an operating time correction unit 22 that outputs a re-registration correction signal through use of a determination period unit.