An air-cooled cooling apparatus for cooling a cooling liquid within a cooling pipe of a refrigeration machine comprising a cooling cycle including a coolant compressor, an air-cooled condenser, an expansion valve, and a cooler, thereby cooling liquid of the refrigeration machine. The apparatus also comprises an air-cooled heat exchanger, outdoor-temperature sensors and three-way valves for controlling the flow of the cooling liquid to be cooled. When the outdoor temperature is high, the cooling liquid is supplied to the cooler, and when the outdoor temperature is low, the compressor is shut down and the cooling liquid is isolated from the cooler and supplied to the heat exchanger to be cooled by cold outdoor air.