Abstract: An apparatus for cooling brine comprising a plurality of refrigerating units connected to a slow-current tank for brine in such a manner said refirgerating units are associated with successive portions of brine in said slow-current tank from the downstream side to the upstream side of said tank, one by one. The number of said refrigerating units taking part in the cooling work is increased and decreased in accordance with the temperature of said brine in said slow-current tank. The connection of said refrigerating units is selectively switched from series to parallel and vice versa with one another, with respect to the brine flow in said slow-current tank. Said means for switching the connection of said refrigerating units from series to parallel and vice versa are constituted by fluid element type shunting devices.