A control device for an internal combustion engine according to the present embodiment, includes: cooling units 40L and 40R arranged on a path where a coolant is circulated, and cooling an exhaust gas of the internal combustion engine with the coolant flowing through the cooling units 40L and 40R; and ECUs 7L and 7R estimating a heat quantity of the exhaust gas, and deciding whether or not to prohibit an idle reduction control in response to the estimated heat quantity of the exhaust gas.