A controller for an absorption cold/hot water generating machine, in which a refrigerating cycle is formed by pipe-connecting an evaporator, an absorber, a solution heat exchanger, a low-temperature generator, a condenser, and a high-temperature generator, and the solution level in a header of the high-temperature generator is kept within a prescribed range by controlling the flow rate of the solution fed from the absorber to the high-temperature generator; wherein a solution pump for feeding a solution from the absorber to the high-temperature generator is inverter-driven, and there is provided pressure difference detecting means for detecting a difference in pressure between the high-temperature generator and the absorber; and wherein there is provided control means which controls the solution pump driving frequency of the inverter as a function of a pressure difference between the high-temperature generator and the absorber.