An electric valve is provided in a supply pipe. A flow rate control unit controls the degree of opening of the electric valve such that the flow rate in the supply pipe lies within a predetermined range, on the basis of a pressure difference between pressure of refrigerant supplied to the supply pipe and the pressure of refrigerant on the suction side of a compressor. An outdoor air temperature sensor detects outdoor air temperature; and a low-pressure side pressure sensor detects refrigerant pressure on the suction side of the compressor. The pressure difference is a difference between a saturation pressure corresponding to the outdoor air temperature detected by the outdoor air temperature sensor and refrigerant pressure detected by the low-pressure side pressure sensor.