The present invention discloses an apparatus and method for varying a usable band range of a battery. The apparatus for varying a usable band range of a battery according to the present invention comprises a sensor for measuring and outputting an electrical characteristic value of the battery; and a controller for calculating the amount of charged or discharged energy of the battery from the electrical characteristic value and varying a usable band range of the battery that is charged and discharged, to maintain the pre-established amount of usable energy depending on the degradation degree of the battery. In accordance with the present invention, a usable band range of a battery can be established depending on the degradation degree of the battery, thereby improving the life time thereof.