PURPOSE: To reduce the refrigerant emission into the atmosphere and shorten the maintenance period of time when refrigerant is filled.

CONSTITUTION: A valve 55 with a gas filling port 56 is mounted on a refrigerant circulation circuit. A gas cylinder 62 is connected to the port 56 via a solenoid valve 61. A controller 60 opens the solenoid valve 61 until an input amount detected by an input amount detector 48 becomes a reference input amount corresponding to the compression ability or larger. When a gas shortage occurs, the gas cylinder 62 is connected to the gas filling port 56 of the valve 55 via the solenoid valve 61. The solenoid valve 61 is opened by the controller 60 and refrigerant gas is filled from the gas cylinder 62 into the refrigerant circulation circuit through the port 56. The solenoid valve 61 is kept open until the input amount detected by the input amount detector 48 becomes a reference input amount corresponding to the compression ability or larger.