Abstract: In a vacuum pumping system, respective pumping assemblies for the reaction chamber and for the load lock chamber are separated from each other, and thereby the degree of vacuum in the reaction chamber is prevented from being degraded. The vacuum pumping system has a cryo pump for pumping the reaction chamber to have a first high degree of vacuum. A first pumping assembly pumps the load lock chamber to have a high degree of vacuum, and a second pumping assembly prevents the first high degree of vacuum from being degraded by pumping the reaction chamber. The second pumping assembly is separated from the cryo pump and the first pumping assembly so as to prevent the reaction chamber and the load lock chamber from being incorporated into one chamber when a wafer passes into and out of the reaction chamber.