Disclosed is an apparatus for controlling the connection of a plurality of battery packs including a switching unit provided on a charge/discharge path of each battery pack to selectively open and close the charge/discharge path, a first control unit provided for each battery pack to determine the state of charge (SOC) of each battery pack and control the opening/closing of the switching unit, and a second control unit to receive the determined SOC of each battery pack from the first control unit, group battery packs having a predetermined range of SOCs, select a group containing a largest number of battery packs, connect the battery packs of the selected group in parallel, charge or discharge the parallel-connected battery packs so that a difference in SOC between the parallel-connected battery packs and the non-connected battery pack falls within a predetermined range, and connect the non-connected battery pack thereto in parallel.