A film-forming apparatus includes a processing chamber, and TiCl4 gas and NH3 gas are supplied into the processing chamber for forming a TiN film on a substrate W in the processing chamber by CVD. The processing chamber has a gas exhaust system. The gas exhaust system includes a gas exhaust pipe for exhausting the exhaust gas in the processing chamber a trap mechanism provided to the gas exhaust pipe for trapping a by-product in the exhaust gas, and a heated reaction gas supply mechanism for supplying a heated reaction gas into the exhaust gas. The heated reaction gas is adapted to react with a component in the exhaust gas to produce a by-product. Specifically, NH3 gas is supplied by the heated reaction gas supply mechanism as the heated reaction gas, and NH4Cl is produced as the by-product.