A method includes forming a film on a substrate by performing a cycle a predetermined number of times, the cycle including non-simultaneously performing: (a) forming a first layer by supplying a precursor to the substrate; and (b) forming a second layer by supplying a reactant to the substrate and modifying the first layer. The (a) includes: (a-1) supplying the precursor to the substrate from a first supply part while supplying an inert gas at a first flow rate, and supplying an inert gas at a second flow rate from a second supply part; and (a-2) supplying the precursor to the substrate while supplying the inert gas at a third flow rate from the first supply part, or supplying the precursor from the first supply part while stopping the supply of the inert gas, and supplying the inert gas at a fourth flow rate from the second supply part.