A liquid cooling device having a diversion mechanism, connected with a heat source, includes a thermoelectric cooler, a first water block, a second water block and a pump. The thermoelectric cooler has a cold end and a hot end. The first water block is disposed between the heat source and the cold end of the thermoelectric cooler. The second water block is disposed on one side of the hot end of the thermoelectric cooler. The pump connects the first water block and the second water block via a water pipe. Thereby, the temperature of an inner fluid is reduced and the overall heat dissipation effect of the device is improved.