A heat dissipation device includes a first heat sink, a second heat sink juxtaposed with the first heat sink and a plurality of heat pipes thermally connecting the first heat sink and the second heat sink. The first heat sink includes a plate-like spreader used for contacting with a first electric component and a honeycomb-like first fin unit thermally attached on the spreader. The spreader is a flat heat pipe. The heat pipes each include a flat plate-shaped evaporating section sandwiched between the spreader and the first fin unit of the first heat sink and a condensing section extending in the second heat sink. Due to a provision of the honeycomb-like first fin unit, the heat dissipation area of the first heat sink greatly increases.