A liquid cooling device includes a hollow heat absorbing unit (2) containing liquid therein, a first heat exchange body (32) and a second heat exchange body (34). The first heat exchange body defines isolated first and second rooms (330, 331) therein. The second heat exchange body defines flow-communicated first and second chambers (350, 351) therein. The first chamber is communicated to the first room, and the second chamber is communicated to the second room. The liquid cooling device further includes a pump (4) fluidly connected between the heat absorbing unit and the second room, and a pipe (7) fluidly connecting the heat absorbing unit and the first room.