A cooling system for a portable computer can include a frame having a heat-source connecting unit in its one side and having a fan housing unit in its other side. A dissipating unit on one side of the fan housing unit performs heat exchange and a dissipating fan forms an air stream that can pass through the dissipating unit. A plate-shaped cooling unit coupled to one side of the frame can deliver heat from the heat-source connecting unit to the dissipating unit. The cooling unit can include a micro cooling unit that performs heat exchange using a cooling cycle through phase change or a plate-heat pipe filled with liquid. According to embodiments of the present invention, a thickness of the cooling system can be reduced and cooling capability efficiency can be increased.