A newly-purchased gas appliance is detected and reported to a gas administrator. There are provided a flow rate detection portion, a flow rate calculation portion, a code extraction portion, an initial code learning portion, a code maintaining portion, a code judging portion, an additional code learning portion, and an external communication portion. The code extraction portion extracts a code pattern E. The initial code learning portion gathers similar code patterns E as a gas appliance code pattern F. The code judging portion judges whether or not the code pattern E matches any of gas appliance code patterns F held by the code maintaining portion within a predetermined range. The code patterns E that have failed to match are subjected to additional identification of a gas appliance in the additional code learning portion. The gas cut-off device can thereby let the additional code learning portion detect whether or not a new gas appliance has emerged and the external communication portion send a report to the gas administrator.