A keypad battery pack, a mobile terminal available for different keypad battery packs, and a method for changing a keypad of a mobile terminal by replacing a battery pack with a different battery pack are provided. The mobile terminal has a keypad formed on a battery pack as well as on a front surface of the mobile terminal, thereby expanding a keypad-placement area to a rear surface of the mobile terminal. As a result, keys of the keypad are arranged on both surfaces of the mobile terminal, and thus a key arrangement space has room for an additional key, thereby enabling easy adding of a key. Further, the keypads of the mobile terminal are arranged on the rear surface and the front surface according to functions of the keypads, thereby providing a keypad structure suitable for a mobile terminal having an additional function. Further, the mobile terminal may selectively mount a plurality of battery packs having different types and arrangements of keypads.