A liquid cooling apparatus for cooling an inversely mounted electronic component, includes a casing defining a receiving room therein, a diaphragm, a partition plate forming a nozzle thereon, and a piezoelectric element attached to the diaphragm in such a manner that a vibrating direction thereof is perpendicular to the diaphragm. The diaphragm is arranged in the receiving room and divides the receiving room into a top first chamber and a bottom second chamber isolated from each other. The partition plate is arranged in the first chamber and divides the first chamber into an upper region and a lower region. The lower region is filled with a working fluid. When the diaphragm is driven to vibrate upwardly by the piezoelectric element, the diaphragm pushes the working fluid in the lower region of the first chamber to the upper region of the first chamber via the nozzle.