A heat dissipation device includes a heat sink assembly, a fan holder and two fans mounted on the two sides of the fan holder. The heat sink assembly includes a heat spreader for contacting with a heat-generating electronic component, and a fin assembly thermally connecting with the heat spreader. The fin assembly has a plurality of channels therein. The fan holder includes a top plate mounted on a top of the fin assembly and a pair of vertical baffle walls extending from two opposite ends of the top plate. The baffle walls of the fan holder are located at two lateral ends of the fin assembly and sandwich the fin assembly therebetween. The two fans respectively abut against inlets and outlets of the channels of the fin assembly. An airflow generated by one fan flows through the fin assembly and is sucked by the other fan.