To provide an engine cooling device having a control valve 23 for circulating coolant between inner passages (4, 5) and outer passages (7, 8) of an engine 1, and permitting or regulating the circulation of the coolant in the inner passages, configured to prevent unnecessary components from being added, and to prevent a significant increase in facility cost by simplifying a process for determining a failure of the control valve 23 as much as possible.

A control part 100 for controlling opening and closing of a control valve 23 is configured to determine whether the control valve 23 has failed, on the basis of a difference between a coolant temperature thw2 in en engine 1 and a coolant temperature thw3 outside the engine 1, after issuing an instruction to open or close the control valve 23.