PURPOSE: To raise the operating ratio of a device by a method wherein at least two high-vacuum exhaust systems including cryopumps, etc. are provided in one vacuum chamber and thereby the regenerative processing time for cryopumps in operation is made unnecessary.

CONSTITUTION: In one vacuum chamber 1 are provided at least two high-vacuum exhaust systems containing cryopumps 2 and 2', gate valves 5 and 5' and fore valves 7 and 7' and changeable independently into the exhaust operation of the vacuum chamber 1 or the regenerative processing of the cryopumps 2 and 2'. Thus, while regenerative processing for one of cryopumps 2 and 2' is performed, the exhaust in the vacuum chamber 1 is conducted by the other. In the case of said application, the down time of the vacuum chamber 1 can be made zero by employing the cryopumps 2 and 2' alternately.