A heat dissipation device includes a heat sink having a plurality of fins defining a plurality of passageways therebetween. The passageways have an inlet and an outlet at two sides of the heat sink. A fan is located at the inlet of the passageways of the heat sink for providing airflow to the heat sink. A guiding member is positioned at the outlet of the passageways of the heat sink for guiding the airflow to electronic components around the heat dissipation device. The heat sink defines a slot at a side thereof, the guiding member extends at least a fixing arm fixed to the heat sink and a tongue embedded into the slot of the heat sink, thereby attaching the guiding member to the heat sink.