A condensing device and a thermal module using same are disclosed. The condensing device includes a hollow main body having a first inlet, a first outlet, and a flow-guiding zone. In the flow-guiding zone, there is provided a plurality of spaced flow-guiding members to define at least one flow passage therebetween. The at least one flow passage is communicable at two opposite ends with the first inlet and the first outlet. The thermal module is formed by connecting the first inlet and the first outlet of the condensing device to a second outlet and a second inlet of a heat-absorption unit, respectively, via two separate heat-transfer units. With the flow-guiding zone provided in the condensing device, it is able to accelerate the vapor-liquid circulation in the condensing device to thereby provide upgraded heat transfer efficiency.