Abstract: The present invention provides an apparatus for cooling an internal combustion engine having a supercharger attached thereto, wherein the apparatus includes communication passages and by way of which the upper end of a coolant flow passage for circulating coolant through the internal combustion engine and a coolant flow passage for circulating coolant through the supercharger communicates with an upper tank installed on a radiator so that cooling of the supercharge and separating of air from coolant can simultaneously be accomplished by arranged of the communication passages.