To provide a liquid warming/temperature-reducing system requiring treating a liquid to be treated 4 by warming, reducing a temperature of the treated liquid, and capable of improving thermal efficiency.

The liquid warming/temperature-reducing system comprises: feeding the treated liquid 1 after warming to an evaporator 2, evaporating the fed treated liquid 1 by flash evaporation, and reducing the temperature of the treated liquid 1; and directly feeding steam of the treated liquid 1 generated in the evaporator 2 and the liquid to be treated 4 to a contact heat exchanger 5, condensing the steam to mix it in the liquid to be treated 4 and warming the liquid to be treated 4.