A rotational speed Cr of a compressor 21 during a defrosting operation is controlled within a control range that corresponds to a capacity ratio P, a total sum Pi of rated capacity of an indoor unit, or a refrigerant pipe length Lr. Accordingly, even in the case where a refrigerant circulation amount during the defrosting operation is reduced due to an installation state of an air conditioner 1, it is possible to prevent suction pressure from being significantly reduced and falling below a performance lower limit value of the compressor 21. Thus, damage to the compressor 21 can be prevented. In addition, it is possible to prevent a case where the suction pressure falls below the performance lower limit value of the compressor 21 and thus low-pressure protection control is executed. Therefore, a case where the restoration of the heating operation is delayed does not occur.