An engine coolant circuit circulating coolant to cool an engine includes: a plurality of thermostatic switching valves disposed in parallel in passages leading from a coolant outlet of the engine; electrically driven three-way valves disposed downstream from the respective thermostatic switching valves in terms of a circulating direction of the coolant; and a radiator and an engine waste heat recovery device disposed in parallel in passages leading from coolant outlets of the electrically driven three-way valves, each one of the electrically driven three-way valves being provided with two coolant outlets, having one of the two coolant outlets thereof configured to communicate with the radiator, and having another one of the two coolant outlets thereof configured to communicate with the engine waste heat recovery device.