An apparatus for battery module balancing, configured to balance a plurality of battery modules (100, 200) that respectively include cell assemblies (10, 20) having at least one secondary battery and electrically connected in series, the apparatus for battery module balancing comprising: a monitoring unit (110; 210) provided to each battery module and configured to monitor at least one of voltage, temperature and current of each cell assembly; a self-circulating path provided to each battery module and electrically connected to both ends of each cell assembly to form a closed circuit, the self-circulating path having an inductor (151; 251) configured to allow a charging and discharging current to flow on the self-circulating path and a first discharge MOSFET (152; 252) configured to open or close the self-circulating path; a connector (120; 220) provided to each battery module and configured to have a plurality of connection terminals (121, 122; 221, 222); a connection path (L2, L3) provided to each battery module to electrically connect both ends of the inductor to the plurality of connection terminals and electrically connect neighboring battery modules to each other through the plurality of connection terminals, the connection path having a second discharge MOSFET (161; 261) provided on the connection path to open or close the connection path; and a processor (130, 230) configured to receive a state of each cell assembly from the monitoring unit and control opening and closing operations of the first discharge MOSFET and the second discharge MOSFET on the basis of the received state of each cell assembly so that the plurality of battery modules are balanced; characterised in that the connection path includes a first internal connection path and a second internal connection path, and the plurality of connection terminals include a first connection terminal and a second connection terminal, wherein the first internal connection path is configured to electrically connect a node between a positive electrode terminal of each cell assembly and one end of the inductor directly to the first connection terminal, and wherein the second internal connection path is configured to electrically connect a node between the other end of the inductor and the first discharge MOSFET directly to the second connection terminal. a monitoring unit (110; 210) provided to each battery module and configured to monitor at least one of voltage, temperature and current of each cell assembly; a self-circulating path provided to each battery module and electrically connected to both ends of each cell assembly to form a closed circuit, the self-circulating path having an inductor (151; 251) configured to allow a charging and discharging current to flow on the self-circulating path and a first discharge MOSFET (152; 252) configured to open or close the self-circulating path; a connector (120; 220) provided to each battery module and configured to have a plurality of connection terminals (121, 122; 221, 222); a connection path (L2, L3) provided to each battery module to electrically connect both ends of the inductor to the plurality of connection terminals and electrically connect neighboring battery modules to each other through the plurality of connection terminals, the connection path having a second discharge MOSFET (161; 261) provided on the connection path to open or close the connection path; and a processor (130, 230) configured to receive a state of each cell assembly from the monitoring unit and control opening and closing operations of the first discharge MOSFET and the second discharge MOSFET on the basis of the received state of each cell assembly so that the plurality of battery modules are balanced; characterised in that the connection path includes a first internal connection path and a second internal connection path, and the plurality of connection terminals include a first connection terminal and a second connection terminal, wherein the first internal connection path is configured to electrically connect a node between a positive electrode terminal of each cell assembly and one end of the inductor directly to the first connection terminal, and the connection path includes a first internal connection path and a second internal connection path, and the plurality of connection terminals include a first connection terminal and a second connection terminal, wherein the first internal connection path is configured to electrically connect a node between a positive electrode terminal of each cell assembly and one end of the inductor directly to the first connection terminal, and wherein the second internal connection path is configured to electrically connect a node between the other end of the inductor and the first discharge MOSFET directly to the second connection terminal.