An apparatus and method for displaying battery capacity and a charge/discharge state of a portable device are provided. The apparatus includes a charge Integrated Circuit (IC) for providing current to recharge the battery using an external charge power source, a sensing resistance interposed between the battery and the charge IC, a switch connected to the sensing resistance in parallel and opened to flow the current to the sensing resistance when a capacity of the battery is measured, and a controller for determining the capacity of the battery using voltage values at both ends of the sensing resistance measured when the switch is opened.