An outdoor unit control unit 200 has a defrosting operation condition table 300a that defines an activation rotational speed Cr in accordance with a total sum of flow rate coefficients Cva that is a total sum of flow rate coefficients Cv representing capacities of indoor expansion valves 52a to 52c. The outdoor unit control unit 200 calculates the total sum of the flow rate coefficients Cva by adding the flow rate coefficient Cv of each of the indoor expansion valves 52a to 52c, and refers to the defrosting operation condition table 300a, so as to determine the activation rotational speed Cr. Then, the outdoor unit control unit 200 activates a compressor 21 at the determined activation rotational speed Cr when starting a defrosting operation, maintains this activation rotational speed Cr for a predetermined time from the start of the defrosting operation, and drives the compressor 21.