Provided is processing of a substrate including: forming film on substrate by performing cycle, multiple times, including non-simultaneously performing: (a) supplying precursor gas and inert gas to the substrate; and (b) supplying reaction gas to the substrate. In (a), at least one of the precursor and inert gas stored in first tank is supplied to the substrate, and at least one of the precursor and inert gas stored in second tank is supplied to the substrate. A concentration of the precursor gas in the first tank differs from that in the second tank. Further, in (a), the at least one of the precursor and inert gas is supplied from the first tank to the substrate, and the at least one of the precursor and inert gas is supplied from the second tank to the substrate to suppress multiple adsorption of molecules constituting the precursor gas on the substrate's surface.