Supercritical refrigeration equipment

PROBLEM TO BE SOLVED: To provide a supercritical refrigeration unit having a bypass device capable of preventing pressure difference between high pressure and low pressure of a high stage side compressor from increasing and a heat pump water heater using such a supercritical refrigeration unit. SOLUTION: A two-stage compressor 11 having a low stage side compressor 11a and the high side compressor 11b as its components, a high pressure side heat exchanger 12 for cooling gas discharged from the compressor 11b of the compressor 11, an expansion device 13 and an evaporator 14 for effecting heat exchange with outdoor air are connected sequentially so as to form a refrigerant circuit to turn high pressure side pressure into a supercritical state. The refrigerant circuit is provided with a bypass circuit 16 so as to bypass to the discharge side of the low stage side compressor the high pressure refrigerant which has been cooled in the high pressure side heat exchanger when outdoor temperature becomes low.