In the present embodiment, in the production of a heat-resistant composite material resulting from impregnating a ceramic fiber preform with silicon carbide, a mixed gas containing starting material gas, an additive gas, and a carrier gas is supplied to a substrate having a minute structure such as a preform stored in an electric furnace, silicon carbide is deposited to form a film by means of a chemical vapor deposition method or a chemical vapor infiltration method, and the film formation growth speed and embedding uniformity are controlled by means of the amount of additive gas added to the starting material gas, the starting material gas contains tetramethylsilane, and the additive gas contains a molecule containing chlorine such as methyl chloride or hydrogen chloride. The film formation growth speed and embedding uniformity of the silicon carbide are both achieved.