A refrigeration cycle apparatus has a refrigerant circuit A. The refrigerant circuit A comprises a compressor 11, a refrigerant passage 12a of a radiator 12 as a water heating heat exchanger, a high pressure side refrigerant passage 15a of internal heat exchanging means 15, a decompressor 13, an evaporator 14, and a low pressure side refrigerant passage 15b of the internal heat exchanging means 15. In the refrigeration cycle apparatus, a pressure detecting apparatus 24 detects that a high pressure side pressure rises to about design pressure, a first solenoid valve 17 provided in a bypass circuit 16 is controlled, by a solenoid valve control apparatus 25, so as to be closed, a low pressure side refrigerant is allowed to flow into the low pressure side refrigerant passage 15b between an outlet of the evaporator 14 and an inlet of the compressor 11, a high pressure side refrigerant flowing through the high pressure side refrigerant passage 15a between an outlet of the radiator 12 and an inlet of the decompressor 13 is cooled, thereby reducing a high pressure side pressure.