There is provided a technique that includes: (a) supplying aminosilane-based gas to a substrate having a surface on which first and second bases are exposed, to adsorb silicon contained in the aminosilane-based gas on a surface of one of the first and second bases; (b) supplying fluorine-containing gas to the substrate after the silicon is adsorbed on the surface of the one of the first and second bases, to react the silicon adsorbed on the surface of the one of the first and second bases with the fluorine-containing gas to modify the surface of the one of the first and second bases; and (c) supplying film-forming gas to the substrate after the surface of the one of the first and second bases is modified, to form a film on a surface of the other of the first and second bases different from the one of the first and second bases.