PURPOSE: To allow a pressure relief valve to be fitted in an optimum direction in the position where a pump is fitted so as to improve the maintainability of the pressure relief valve after the regeneration of a cryopump.

CONSTITUTION: An exhaust pipeline 15 at the regenerating time of a cryopump is removable. The exhaust pipeline 15 has a flange 11 with an even number of holes opened in symmetry in order to be fitted to a cryopump body 12. With the threaded holes well-fitted and except the direction of a motor 17, the direction of the exhaust pipeline 15 can be changed optionally. A pressure relief valve is thereby fitted in an optimum direction in the position where a pump is fitted.