An absorption heat pump apparatus using a refrigerant as a heat exchanging medium includes a vapor generator for producing a dilute refrigerant solution and a heat exchanger having an evaporator for producing evaporated refrigerant gas and an absorber for making the evaporated refrigerant gas to be absorbed into the dilute refrigerant solution. A plurality refrigerant paths extending inside the evaporator and absorber for flowing the refrigerant inside for heat exchange operation. Each inlet end of refrigerant paths is connected to an inlet before the evaporator by a plurality of first capillary paths. Each outlet end of refrigerant paths is joined to an outlet. A plurality of second capillary paths are connected to the refrigerant paths before the absorber for supplying the dilute refrigerant solution to the absorber. When passing through the capillary paths, the refrigerant is cooled due to the pressure loss.