A battery management system and a driving method thereof to manage a battery including a plurality of cells. The battery management system includes a sensing unit, an MCU, and a cell balancing unit. The sensing unit measures cell voltages of the plurality of cells. The MCU detects cells requiring cell balancing according to the plurality of measured cell voltages and generates a plurality of cellvoltage signals to control the cell balancing of the detected cells. The cell balancing unit balances the cells according to the plurality of cell voltage signals, and the number of the cell voltage signals is fewer than the number of cells. The cell balancing unit generates a plurality of cell balancing signals corresponding to each of the plurality of cell voltage signals, and at least one of the cell voltage signals balances at least two of cells in the battery.