A liquid cooling device includes a heat-dissipating member, a driving member and a heat-absorbing member connected together to form a heat transfer loop. A coolant is filled in the heat transfer loop. The heat-absorbing member defines therein a receiving chamber. A heat sink and a heat pipe are received in the receiving chamber. The heat pipe thermally connects the heat sink to a heat-absorbing plate of the heat-absorbing member. The heat-absorbing plate is used for contacting with a heat-generating component. The coolant is driven by the driving member to circulate between the heat-absorbing member. Heat generated by the heat-generating component is absorbed by the heat-absorbing plate and transferred to the heat sink via the heat pipe. The heat sink releases the heat to the coolant. The coolant takes the heat from the heat-absorbing member to the heat-dissipating member for dissipating.