A heat dissipating device includes: a barrel having a plurality of fins formed on the barrel and having a buckle for fastening the barrel to a base board of a central processing unit (CPU) to conduct heat from CPU towards the barrel; a cooling fan contiguous to the fins and the barrel for cooling the fins and the barrel; a vaporizable coolant filled in the barrel; a guiding device provided in the barrel for guiding and ejecting the vapor as vaporized from a liquid coolant when absorbing the heat from CPU towards a cooled inside wall of the barrel to be condensed as a liquid coolant; and a capillary device formed on the inside wall for capillarily osmetically draining the liquid coolant towards a bottom of the barrel for enhancing a liquid-vapor two phase recirculation of the coolant for efficiently dissipating heat from the CPU.