A battery charging controlling apparatus for balancing voltages of the charged batteries is provided. The battery charging controlling includes a battery reference voltage generating unit, a voltage balancing unit, and a balance judging unit. The battery charging controlling apparatus determines whether a battery voltage difference between any two adjacent battery units of a battery module is too large or not by using a reference voltage provided from the battery reference voltage generating unit. The battery charging controlling apparatus further detects the voltage of the battery module and a charging current thereto to determine a suitable time for balancing the charged batteries. Then, the voltage balancing unit controlled by the balance judging unit allows the charging current of the lower-voltage battery unit greater than the charging current of the higher-voltage battery, unit so as to lower the battery voltage difference of the battery units.