PURPOSE: To ensure stability of an engine, by raising the supercharging pressure to a proper level by forming a layer of a heat accumulating medium over the outer peripheral surface of a heat exchanging section of an intercooler, accumulating cold heat by cooling the layer of a heat accumulating medium during the operation of the intercooler, and utilizing the cold heat accumulated in said layer as a cold heat source of said heat exchanging section.

CONSTITUTION: An intercooler 20 is disposed at an intermediate portion of an inlet duct 9 connecting a compressor 6 of a turbocharger 4 and an intake manifold 2 of an engine 1. A layer 27 of a heat accumulating medium is cooled by a coolant tube 26, and an inner casing 23 and fins 24 constituting a heat exchanging section 25 are cooled by the layer 27 of a heat accumulating medium by way of heat conduction. By thus exchanging heat, it is enabled to cool air passed through the heat exchanging section positively.