A gas cutoff device, comprising: a flow rate detection unit that is configured to output a flow rate signal in response to a gas flow rate passing through a gas path; a flow rate calculation unit that is configured to calculate a flow rate upon receiving the flow rate signal from the flow rate detection unit; an increase and decrease calculation unit that is configured to compare a previously acquired flow rate with a currently acquired flow rate, and, if there is a change, outputs a change amount; an increase and decrease determination unit which is configured to manage a plurality of change amounts output by the increase and decrease calculation unit while adding and holding the change amount if the change amount is an increase amount, and deleting the nearest held change amount to the decrease amount if the change amount is a decrease amount, to output an increase and decrease processed signal and to extract a usable time of gas based on the greatest held change amount, and when a time of using gas reaches the usable time, output a valve driving signal; a valve driving unit that is configured to output a closing signal upon receiving the valve driving signal from the increase and decrease determination unit; a valve that is configured to close the gas path upon receiving the closing signal from the valve driving unit; and an increase and decrease correction unit which is configured, upon receiving the increase and decrease processed signal, to compare the sum of the plurality of change amounts held in the increase and decrease determination unit with the currently acquired flow rate, and if a flow rate difference is equal to or greater than a predetermined value, to output a corrected change amount obtained by adding or subtracting the calculated flow rate difference to or from the greatest change amount acquired from the increase and decrease determination unit, wherein upon acquiring the corrected change amount, the increase and decrease determination unit deletes the greatest held change amount, holds the corrected change amount as a new change amount, then extracts the usable time of gas based on the new greatest held change amount, and outputs the valve driving signal when the time using gas reaches the usable time. a flow rate detection unit that is configured to output a flow rate signal in response to a gas flow rate passing through a gas path; a flow rate calculation unit that is configured to calculate a flow rate upon receiving the flow rate signal from the flow rate detection unit; an increase and decrease calculation unit that is configured to compare a previously acquired flow rate with a currently acquired flow rate, and, if there is a change, outputs a change amount; an increase and decrease determination unit which is configured to manage a plurality of change amounts output by the increase and decrease calculation unit while adding and holding the change amount if the change amount is an increase amount, and deleting the nearest held change amount to the decrease amount if the change amount is a decrease amount, to output an increase and decrease processed signal and to extract a usable time of gas based on the greatest held change amount, and when a time of using gas reaches the usable time, output a valve driving signal; a valve driving unit that is configured to output a closing signal upon receiving the valve driving signal from the increase and decrease determination unit; a valve that is configured to close the gas path upon receiving the closing signal from the valve driving unit; and an increase and decrease correction unit which is configured, upon receiving the increase and decrease processed signal, to compare the sum of the plurality of change amounts held in the increase and decrease determination unit with the currently acquired flow rate, and if a flow rate difference is equal to or greater than a predetermined value, to output a corrected change amount obtained by adding or subtracting the calculated flow rate difference to or from the greatest change amount acquired from the increase and decrease determination unit, wherein upon acquiring the corrected change amount, the increase and decrease determination unit deletes the greatest held change amount, holds the corrected change amount as a new change amount, then extracts the usable time of gas based on the new greatest held change amount, and outputs the valve driving signal when the time using gas reaches the usable time.