[Problem] The present invention provides a gas supply method by which a gas in a gas container can be effectively utilized.
[Means for solving the problem] On the basis of: the maximum flow rate (a first preset flow rate (Q1)) and the minimum flow rate (a second preset flow rate (Q2)) at the place where the gas is used; a first preset pressure (P1) at which the gas can be supplied at a first preset flow rate (Q1); a second preset pressure (P2) at which the gas can be supplied at a second preset flow rate (Q2); a third preset pressure (P3) which is higher than the first preset pressure (P1); residual pressures (PA, PB) in gas containers (SA, SB); a supplied gas flow rate (Q); and the relationship between the residual pressures (PA, PB) and suppliable gas flow rates (QPA and QPB, respectively), the residual pressures (PA, PB) and the supplied gas flow rate (Q) are monitored and the gas supply is switched between the first gas container (SA) and the second gas container (SB).