To provide a system for boiling washing hot water which is indispensable in a milking machine, using a reduced amount of electricity or petroleum.

The quick cooling system for cow's milk is constituted of an ice storage tank 20, a heat-exchanger 14, a heat-pump device 50 to use a nonfreezing liquid that absorbs heat from the ice storage tank 20 through a heat-transmission tube 37 which is inserted into the ice storage tank 20 as a high-temperature side medium and use water as the low-temperature side medium and transmit the heat of the ice storage tank 20 to the water for obtaining hot water, and a hot water storage tank 32 for holding the hot water, obtained by the heat-pump device 50 and provided with a heater 31 for heating the hot water to a prescribed temperature. The freshly extracted warm milk is cooled rapidly to 4C, and the heat recovered from the milk is used for boiling water. Since the water is heated to about 60C, it can be used as hot water, by only additionally heating to 80C, and significant saving of the electricity bill or the petroleum bill can be made.