A heat dissipating device includes: a barrel having a plurality of fins circumferentially formed on a barrel wall; a buckle secured on a first end portion of the barrel to be fastened to a base board of a central processing unit (CPU); a cooling fan provided at a second end portion of the barrel for directing cooling air through the barrel wall and the fins for dissipating heat outwardly as emitted from the CPU which is adhered to the first end portion of the barrel; a vaporizable coolant filled in the barrel; and a transfer member fixed in the barrel for conducting the heat from the CPU to the vaporizable coolant for vaporizing the coolant in order to greatly absorb a vaporization heat during the phase change from the liquid coolant to the coolant vapor, whereby upon contact of the coolant vapor with the barrel wall as cooled by the cooling fan, the coolant vapor will be condensed to liberate the condensation heat which will soon be dissipated through the barrel wall and the fins by the cooling air as delivered from the fan for efficiently cooling the central processing unit.
