An exemplary heat dissipation device includes a heat pipe and a fin unit. The heat pipe includes an evaporation section and a condensing section formed at opposite ends thereof, respectively. The fin unit includes plural stacked parallel fins. Each of the fins defines a through hole therein for receiving the condensing section of the heat pipe. A flange extends from a periphery of the through hole. The flange defines two slits to divide the flange into two separate portions. The slits communicate with the through hole. A compressible structure is formed in each fin at opposite sides of the through hole. The compressible structure is aligned with the slits such that when the fin is compressed along a direction transverse to the alignment, the compressible structure is compressed and the separate portions of the flange move toward each other and closely contact the condensing section of the heat pipe.