Cooling device for engine

Comprises: a flow rate adjustment unit (12) for adjusting the flow rate of cooling water circulating between an engine (1) and a radiator (9); a water temperature detection unit (17) that detects the temperature of the cooling water flowing through the engine; a water temperature detection unit (21) that calculates a target water temperature of the cooling water; a deviation calculation unit (22) that calculates a water temperature deviation on the basis of the water temperature and the target water temperature; a target opening degree calculation unit (24) that calculates, on the basis of the water temperature deviation, a target opening degree of the flow rate adjustment unit (12) for achieving the target water temperature; an opening/closing direction determination unit (25) that determines the opening/closing direction of the flow rate adjustment unit (12) on the basis of the state of change in the target opening degree; a control speed calculation unit (26) that calculates the control speed of the flow r