A two-stage charge equalization apparatus for a series-connected battery string includes a battery module having a plurality of batteries connected in series; a battery string having M (M≧2) battery modules connected in series; M charge control switch modules connected in parallel to each of the M battery modules; M second DC/DC converters connected to each of the M charge control switch modules; a single first DC/DC converter connected to the M second DC/DC converter; and a microprocessor controlling the charge control switch module, wherein the first DC/DC converter is inputted with an overall potential of the battery string and outputs a potential lower than the potential inputted and each of batteries composing the battery module shares the second DC/DC converter using the charge control switch module.