To improve the capability of a heat pump apparatus upon heating operation without making the heat pump apparatus large-sized by providing a heater on a refrigerant circuit.

Temperature of a refrigerant passing through a refrigerant piping (6) is increased by making use of an electric heater provided between an indoor heat exchanger (2) of a refrigerant circuit and expansion means (4). As a result, load of heating capability of an outdoor heat exchanger (5) is reduced to prevent the outdoor heat exchange (5) from becoming large-sized.