A heat dissipation device includes a first heat sink thermally contacting an electronic component, a second heat sink connecting to the first heat sink, and a heat pipe thermally connecting the first heat sink with the second heat sink. The first heat sink defines a receiving portion at a lateral side thereof. The heat pipe includes an evaporating section attached to the first heat sink, a condensing section attached to the second heat sink and a connecting section interconnecting the evaporating section with the condensing section. An engaging portion protrudes from a lateral side of the second heat sink and is firmly embedded in and lockable with the receiving portion of the first heat sink. The heat pipe extends through the engaging portion.