To prevent efficiency from decreasing when the flow rate of cooling water is reduced in partial loading by controlling the rotation of an absorption pump for feeding an absorption liquid from an absorber to a reproducer based on the size of a thermal load and the amount of heat that the cooling water being supplied to the absorber and a condenser preserved.

In an absorption refrigerating machine where a high-temperature reproducer 1, a low-temperature reproducer 2, a condenser 3, an evaporator 4, an absorber 5, and the like are connected, fluid that is cooled by the evaporator 4 where a refrigerant is evaporated is supplied to a thermal load. In this case, the temperature of cold water being supplied from the evaporator to the thermal load is detected by a temperature sensor S2 and the heating power of a combustion device 1B is adjusted so that its cold water temperature T2 reaches a specific low temperature. Also, the rotation of an absorption liquid pump P1 is controlled based on an absorption liquid temperature T3 in the high-temperature reproducer 1 being detected by a temperature sensor S3, a cooling water temperature T4 being detected by a temperature sensor S4, and the flow rate of cooling water being detected by a flow rate sensor S5.