An object of the invention is to avoid a gap between the total using amount of gas and the sum of a plurality of change amounts held in a gas cutoff device. The gas cutoff device includes a flow rate detection unit 11, a flow rate calculation unit 12, an increase and decrease calculation unit 13, an increase and decrease determination unit 14, a valve driving unit 15, a valve 16, an increase and decrease correction unit 17, and a constant increase and decrease correction unit 18. The increase and decrease determination unit 14 acquires a corrected change amount 'G' from the increase and decrease unit 17 or the constant increase and decrease correction unit 18 and adopts the amount as a new change amount 'C'. In this way, it is possible to prevent the using time of gas until the gas path is closed from being lengthened.