Engine system

Provided is an engine system in which the wall temperature of a combustion chamber is adjusted with high responsiveness in accordance with the load of an engine. An engine system (1) is provided with an engine (10), a circulation device (91) for circulating cooling water through a water jacket (20), and a controller (ECU (100)). The circulation device has a radiator flow path (53) including a heat exchanger (radiator (27)), a bypass flow path (51), a flow rate adjustment device (cooling water control valve (4)), and a thermostatic valve (28). When the load of the engine is lower than a first load, the controller controls the flow rate adjusting device so as to adjust the flow rate of the cooling water flowing through the water jacket according to the load by closing the radiator flow path and adjusting the flow rate of the cooling water flowing through the bypass flow path, and when the load is equal to or greater than the first load, the controller controls the flow rate adjusting device so as to adjust the