A control device for an absorption refrigeration machine in which an evaporator, an absorber, an absorption liquid pump, a generator and a condenser, etc. are connected to form a refrigeration cycle. A heating amount of the generator is controlled on the basis of external conditions or internal conditions. The device includes a detection device for detecting a plurality of change amounts representative of the external conditions or internal conditions. A memory device stores fuzzy rules and membership functions between the change amounts and a rotational speed of the absorption liquid pump. An arithmetic unit carries out fuzzy logical calculations based on the change amounts and the fuzzy rules and membership functions to calculate the rotational speed of the absorption liquid pump. A control device inputs an output of the arithmetic unit to control the rotational speed of the absorption liquid pump.