A heat dissipation device includes a spreader, a heat sink comprising a base plate and a plurality of outer fins extending upwardly from a top surface of the base plate, a heat pipe thermally connecting the heat sink and the spreader together, a plurality of fasteners each including a fixture having a head at a top thereof, a spring encircling the fixture and a gasket wired on the fixtures. The fixtures extend through the base plate of the heat sink and the spreader, the gaskets are respectively compressed between the heads and the base plate, edge of the base plate of the heat sink is joined with the housing of the computer, and cooperates with the housing to form a hermetic encapsulation which encloses the heat-generating electronic component.