The present disclosure provides a method for adsorption/desorption of lithium ions from brine, which employs a counter current decantation process in adsorption/desorption of lithium ions, thereby achieving an adsorption rate of 65 ± 5% and a desorption rate of 95 ± 3%. The method includes supplying brine into one of a plurality of adsorption reactors, adsorbing lithium ions to an adsorbent by supplying the adsorbent to the adsorption reactor to which the brine is supplied and forcing the brine and the adsorbent to sequentially flow backwards inside the respective adsorption reactors, and desorbing the lithium ions from the brine by forcing the adsorbent to which the lithium ions are adsorbed to sequentially flow backwards inside a plurality of desorption reactors. Here, the brine and the adsorbent are stirred by a stirrer to maintain the adsorbent in an intermediate state instead of settling or floating inside the respective adsorption reactors, after supplying the adsorbent to the adsorption reactor to which the brine is supplied.