A heat dissipation device includes a first base plate having a flat top surface, a plurality of flattened heat pipes, a fin assembly located above the heat pipes and a thermally conductive layer formed between the heat pipes and the fin assembly. The thermally conductive layer has a flat surface contacting with the heat pipes. The heat pipes are supported on the top surface of the first base plate. The first base plate has a flat bottom surface for engaging with an electronic package. Each heat pipe comprises an evaporating section and a condensing section bent from the evaporating section, and the evaporating sections of the heat pipes abut side by side against each other.