A heat dissipation device includes a heat sink (10) in thermal contact with a first heat-generating electronic component. A fan duct (30) receives the heat sink therein and has an inlet (350) and an outlet (302) at opposite sides thereof. A fan (20) is mounted in the fan duct at the inlet. A portion of airflow generated by the fan flows through the heat sink to cool the first heat-generating electronic component. A shutter (31) is mounted on the fan duct. Another portion of the airflow generated by the fan flows through the shutter to blow a second heat-generating electronic component located beside the first heat-generating electronic component and outside the fan duct.