PURPOSE: To provide a heat pump device driven by an engine in which the cost can be reduced with a simple structure, procuring of an installation space is easy, and pressure loss of refrigerant stream can be reduced.

CONSTITUTION: A heat pump device driven by engine 1 is provided with a hot water circuit 7 to cool an engine 5 by circulation of cooling water, a refrigerant circuit 6 to cool and heat by circulation of refrigerant, a heat exchanger 26 placed adjacent to the refrigerant circuit 6 and the hot water circuit 7 to exchange heat between these circuits 6 and 7, a compressor 4 to circulate refrigerant in the refrigerant circuit 6, and the engine 5 to drive the compressor 4. In this instance, a part of the refrigerant circuit 6 is formed integrally with the heat exchanger 26 in a plate-shaped circuit unit A.