An absorption heat pump apparatus using a refrigerant (RF) as a heat exchanging medium includes a vapor generator (4) for producing a dilute refrigerant solution (RF') and a heat exchanger (100) having an evaporator (12) for producing evaporated refrigerant gas and an absorber (17) for making the evaporated refrigerant gas to be absorbed into the dilute refrigerant solution (RF'). A plurality refrigerant paths (25) extending inside the evaporator (12) and absorber (13) for flowing the refrigerant (RF) inside for heat exchange operation. Each inlet end of refrigerant paths (25) is connected to an inlet (23) before the evaporator (12) by a plurality of first capillary paths (18). Each outlet end of refrigerant paths (25) is joined to an outlet (27). A plurality of second capillary paths (18) are connected to the refrigerant paths (25) before the absorber (17) for supplying the dilute refrigerant solution (RF') to the absorber (17). When passing through the capillary paths (13 and 18), the refrigerant (RF and RF') is cooled due to the pressure loss.