REFRIGERATION AND AIR-CONDITIONING DEVICE

To provide a refrigerating and air-conditioning apparatus that is capable of, even during a heating operation under air conditions leading to formation of frost, performing a defrosting operation while simultaneously continuing the heating operation and that improves comfort through heating by securing an appropriate amount of ventilation. A plurality of refrigeration cycles that are capable of independently performing a heating operation and a defrosting operation, are provided. By controlling a ventilation damper of an indoor unit that is to perform a defrosting operation to increase the amount of ventilation, a prior ventilation operation for securing the time-averaged required amount of ventilation including the period in which the defrosting operation is being performed is performed before the defrosting operation, and after the prior ventilation is terminated, the defrosting operation is started.