To provide a heat pump which can use heat as its driving source and water containing a smaller amount environmental loads as a refrigerant, hardly causes problems, such as the corrosion, etc., can be reduced in size and weight, can be mass-produced, and can be used commonly for refrigerating and heating operations.

A heat pump is constituted, in such a way that a compressor 2 in a compression-type refrigerating cycle is driven by means of a turbine 1 which is driven with refrigerant vapor generated from a generator 4, and the same refrigerant is used as the refrigerant, which drives the turbine 1 and the refrigerant which is compressed by means of the compressor 2.