High temperature (HT) and low temperature (LT) cooling water, the LT cooling water being at a lower temperature than the HT cooling water, circulate in HT and LT cooling water flows in respective channels. A controller controls to set the temperature of the LT cooling water lower in a case where an operating point of an engine lies in a particular region in an operational region of the engine, the particular region including a region in which the load is high and the engine speed is low, than in a case where the operating point lies in an operational region other than the particular region. Furthermore, the controller narrows the particular region in a direction toward higher loads in a case where the temperature of the HT cooling water is lower than a predetermined temperature.