An object of the present invention is to ensure the stable operation of a vacuum pump for discharging an unused source gas and reaction byproduct gases from a low-pressure processing chamber, to recover the reaction byproducts efficiently for the effective utilization of resources and reduction of running costs. A low-pressure CVD system has a processing vessel (10) for carrying out a low-pressure CVD process for forming a copper film, a source gas supply unit (12) for supplying an organic copper compound as a source gas, such as Cu(I)hfacTMVS, into the processing vessel (10), and an evacuating system (14) for evacuating the processing vessel (10). The evacuating system (14) includes a vacuum pump (26), a high-temperature trapping device (28) disposed above the vacuum pump (26) with respect to the flowing direction of a gas, and a low-temperature trapping device (30) disposed below the vacuum pump with respect to the flowing direction of a gas. The high-temperature trapping device (28) decomposes the unused Cu(I)hfacTMVS contained in a gas sucked out of the processing vessel (10) to trap metallic copper. The low-temperature trapping device traps Cu(II)(hfac)₂ produced as a reaction byproduct.