An apparatus for balancing charge capacity of battery cell includes a voltage sensing/discharging circuit having a battery with cell group, a switching unit for selectively connecting both terminals of each battery cell to conductive lines, capacitor connected to the conductive lines, a voltage amplifying unit connected to both terminals of capacitor via a first switch, and a discharge resistance connected to both terminals of capacitor via a second switch; and a voltage balancing unit for controlling the switching unit in ON state of first switch to connect both terminals of each battery cell to the conductive lines and then sense voltage of each battery cell through the voltage amplifying unit, and controlling the switching unit in OFF state of first switch to charge voltage of balancing-requiring cell to the capacitor and then turning on the second switch to discharge charged voltage of capacitor through the discharge resistance.