To contrive not to decrease capacity of a refrigerating machine at a time of a stop of a compressor.

A standby compressor unit 5 is provided in addition to an operation compressor unit 1 for supplying helium gas to a refrigerating machine unit 2 at a time of normal operation. A three port switching valve with electromagnetic operation, a pilot operation, or manual operation is provided at a branch pint A to the standby compressor unit 5 in piping 4. Consequently, in the case of an abnormal stop of the operation compressor unit 1, the standby compressor unit 5 starts instantaneously to allow an MRI unit 3 to operate continuously without lowering refrigerating capacity of the refrigerating machine unit 2, enabling a loss time required for restarting (cooling down) of the refrigerating machine unit 2 to be eliminated.