A miniature liquid cooling device includes a casing (10) having a base (16) attached on a heat-generating electronic component for absorbing heat generated by the electronic component. The casing includes an outer wall (12) mounted on the base and a top cover (15) mounted on the outer wall. A receiving space is enclosed by the casing. A heat-absorbing member (40) is attached on the base and received in the receiving space for exchanging heat with liquid in the casing. An impeller (21) is rotatably mounted in the receiving space and above the heat-absorbing member. When the impeller rotates the liquid is driven to flow into the liquid cooling device via a liquid inlet (122) and then flow through the heat-absorbing member and finally flow out of the liquid cooling device via a liquid outlet (124).