To prevent a gas-liquid two phase refrigerant from flowing into a pressure reducing device and obtain high temperature hot water.

When high temperature hot water is supplied, heat exchange is effected between a high pressure refrigerant flowing into a pressure reducing device 3 and a low pressure refrigerant flowing out from an air heat exchanger 4, and when low temperature hot water is supplied, heat exchange is not effected between the high pressure refrigerant and the low pressure refrigerant. By this method, when heat exchange is effected between the high pressure refrigerant and the low temperature refrigerant, ratio of a gas phase refrigerant occupying a water heat exchanger 2 increases so that high temperature hot water can be obtained. Therefore, even in the case of obtaining high temperature hot water, heat pump cycle for water heating is stabilized since condensed or supercooled liquid phase refrigerant flows into the pressure reducing device 3.