To improve heat exchange efficiency of a heat exchanger of an absorber or the like in an absorption refrigerating machine.

Evaporator tubes 11 of an evaporator 10 and absorber tubes 21 of an absorber 20 are U-tubes and arranged to extend in a vertical direction. Chilled water W1 flows in the tubes 11, and a refrigerant R flowing down on outside circumferential surfaces of the tubes 11 and wetting the same makes heat exchange be conducted between the chilled water W1 and the refrigerant R. Cooling water W2 flows inside the tubes 21, and a lithium bromide solution Y flowing down on outside circumferential surfaces of the tubes 21 and wetting the same makes heat exchange be conducted between the cooling water W2 and the lithium bromide solution Y. At this time, a vertical arrangement of the tubes 11, 21 allows the refrigerant R and the lithium bromide solution Y flowing down on the outside circumferential surfaces to flow down on the whole surfaces of the same wetting the whole surfaces of the same, improving heat exchange efficiency.