COOLING SYSTEM FOR VEHICLE

A first coolant circuit circulates coolant through engine, an exhaust heat recovery device recovers exhaust heat of an in-vehicle heat source and heats coolant passing therethrough, a second coolant circuit circulates coolant through the exhaust heat recovery device, and a coolant temperature sensor detects the temperature of the coolant in the engine. The coolant of the first coolant circuit is mixed with the coolant of the second coolant circuit when the temperature detected by the coolant temperature sensor becomes greater than or equal to a semi-warm-up determination value, which is set to a temperature that is lower than a warm-up completion determination value of the engine. Accordingly, when the heat generated by the engine and the heat recovered by the exhaust heat recovery device from the in-vehicle heat source are independently used to increase the temperature of the coolant, control can be executed without any trouble based on the coolant temperature even when mixing the coolant of the engine with the coolant of the exhaust heat recovery device, in which the temperatures have been increased independently.