Heretofore, there has been known a cooling apparatus for cooling a heat exchanger with a fan driven by an engine. JP, U, 63-4400, for example, discloses a cooling apparatus comprising a heat exchanger, a propeller fan whose rotary shaft is rotated by the driving force of an engine to produce a stream of cooling air for cooling the heat exchanger, and a shroud provided downstream of the heat exchanger for introducing the cooling air to the suction side of the propeller fan, wherein a substantially disk-shaped back plate is provided just behind rotor blades of the propeller fan on the blowoff side, the back plate having almost the same diameter as an outline of the propeller fan. Such a construction is effective to avoid the occurrence of turbulence caused by interference between a main stream of the cooling air produced in the centrifugal direction on the blowoff side of the propeller fan and a reverse stream tending to return toward the heat exchanger side after being separated from the main stream, and hence to reduce noise generated by the fan.