A heat dissipating device includes a fluid container made of a heat conductive material and having a heat-dissipating wall opposite to a heat-absorbing wall, and a surrounding wall cooperating with the heat-absorbing and heat-dissipating walls so as to confine a sealed vapor chamber. A heat exchanger member is disposed in the vapor chamber, is in heat-conductive contact with the heat-absorbing wall, and contains an amount of working fluid capable of changing into fluid vapor that fills the vapor chamber upon absorbing heat from the heat-absorbing wall. The fluid vapor is capable of changing into fluid condensate when cooled due to contact with the heat-dissipating wall. A heat-conductive cover plate is mounted spacedly on the heat-dissipating wall of the fluid container, and cooperates with the heat-dissipating wall so as to confine a heat-dissipating passage therebetween such that heat absorbed by the heat-dissipating wall is dissipated via the heat-dissipating passage.