A tank is provided which can store, while cooling, drinks or other liquids, such as milk, having a storage temperature close to 0.degree. C. or below.A cooling tank (1) can be mounted on a truck or the like for transportation, while storing and cooling milk. It is characterized in that brine (antifreeze solution) which has a freezing point below 0.degree. C. is cooled in a cooling unit (34) and allowed to pass, without stagnation, along fluid passages in flow guide members (14, 18) installed on the wall surface of the tank body (10). The cooling unit (34) preferably has an evaporator in a heat pump type refrigerator (30) for example, which uses a refrigerant for cooling the brine. Since the brine with a freezing point below 0.degree. C. is used, a large-sized water tank for cooling becomes unnecessary, and further since the brine will flow without stagnation, the liquid inside the tank body can be effectively cooled.