Abstract: A vacuum processing system including two or more processing units for processing wafers and a transferring unit for carrying the wafers. In this system, even when any one of the processing units becomes inoperable because of a failure, the operation of the system can be continued, and even when a processing unit in the system requires repair or maintenance at the time of the start of operation, the system can be operated using other operable processing units without subjecting the operator to danger due to improper operation. As a result, the working efficiency of the system can be increased and the safety of the operator can be secured. In this system, the cleaning of the interior of each processing unit is performed by carrying a cleaning dummy wafer into each processing unit using the transferring unit, followed by recovery of the dummy wafer after cleaning, so that processing of wafers in the processing unit can be carried out once again.