PURPOSE: To enable to shorten the time required for removal of gas, by drawing out gas while detecting characteristics of pressure rise in a cryopump and the temperature of a cryopanel.

CONSTITUTION: In case that the pressure rise in a cryopump, detected by a low vacuum gauge 7, is greater than 0.005 Torr/min, it is judged that removal of gas is not completed, and gas is drawn out again by opening a valve 10. when the pressure rise in the pump becomes lower than 0.005 Torr, it is judged that removal of gas has been completed, and the valve 10 is opened again for evacuating the inner space of the cryopump to a level lower than 0.3 Torr. Then, the valve 10 is closed and the cryopump is set into operation. Regeneration of the cryopump is completed by detecting whether the pump has been evacuated completely or not by means of a thermocouple 2.