PURPOSE: To prevent, generation of particules so as to shorten the regenerating time of a cryopump by carrying out exhaust in a pressure level of triple point pressure or less in a cryopump container while heating a second step heat load stage.

CONSTITUTION: A cryopump is stopped while starting regeneration, and electrification of a heater is started. And oxygen gas generated in an engine (a) in which a temperature is raised to about 30K is discharged. A solid argon is sublimated at a (b) part, and it is discharged. When the rest of the solid argon is reduced and an evaporation amount is reduced, a temperature which is reduced from 151k is raised to 151K and more. When the temperature exceeds 273K, ices fuse, and gas purge is carried out by inactive gas so as to discharge water. After moisture is discharged, inactive gas purge is stopped, roughing is carried out in a pressure level which is not interfered with starting of the cryopump (at d part). The cryopump is started, and cooling is started. When a temperature in a second step heat load stage is decreased to 20k and regeneration is completed, regeneration is completed at about 140 minutes.