A heat dissipating apparatus has a phase change material evaporator, a condenser, a refrigerant output tube, and a refrigerant input tube. The evaporator has a base having an evaporation chamber, a refrigerant inlet and a refrigerant outlet, a reinforcement panel mounted in the evaporation chamber and dividing the evaporation chamber into two spaces, and multiple heat conduction fins separately arranged in the two spaces. An opening area of the refrigerant outlet is larger than an opening area of the refrigerant inlet. The evaporator, the refrigerant output tube, the condenser and the refrigerant input tube form a closed refrigerant circulation loop with a refrigerant filled therein. Gas pressure of a gas-phased refrigerant in the two spaces can be increased. With pressure difference between the refrigerant outlet and the refrigerant inlet, the gas-phased refrigerant can be accelerated to flow toward the refrigerant outlet and flowability of the refrigerant can be increased.