Abstract: An air conditioner includes a compressor, four-way valve, outdoor side heat exchanger, expansion valve and indoor side heating exchanger, which components are sequentially connected via coolant tubes, thereby constructing a refrigeration cycle circuit which is capable of performing cooling (defrosting) and heating operations. A switching control valve is connected between the suction side of the compressor and the four-way valve. The control valve is opened when abnormal high pressure is produced in the refrigeration cycle and when the defrosting operation is performed. A first branch passage is connected at its one end between the four-way valve and indoor side heat exchanger, and at the other end to the control valve. During the heating operation, when the control valve is opened, the first branch passage forms a releasing circuit, thereby releasing the abnormal high pressure to the low pressure side of the refrigeration cycle.