A method of manufacturing a passivation film, which includes a passivation process in which a substrate on the surface of which at least one of germanium and molybdenum is contained is treated with a passivation gas containing an oxygen-containing compound, which is a compound containing an oxygen atom in the molecule, and hydrogen sulfide to form a passivation film containing a sulfur atom on the surface of the substrate. The concentration of the oxygen-containing compound in the passivation gas is from 0.001 mole ppm to less than 75 mole ppm.