An apparatus for maintaining a charge amount of a secondary battery, the apparatus comprising: a sensing unit to measure an electrical characteristic value of the secondary battery; a memory unit to store a charged power amount decrease section and a charged power amount increase section based on the electrical characteristic value of the secondary battery; and a control unit to output a control signal for reducing an amount of power charged in the secondary battery when a state of the secondary battery corresponds to the charged power amount decrease section based on the electrical characteristic value measured by the sensing unit, and to output a control signal for increasing an amount of power charged in the secondary battery when the state of the secondary battery corresponds to the charged power amount increase section based on the electrical characteristic value measured by the sensing unit, wherein the charged power amount decrease section is a section where the amount of power charged in the secondary battery is beyond a required charge amount maintenance section, the charged power amount increase section is a section where the amount of power charged in the secondary battery is below the required charge amount maintenance section, and wherein when the state of the secondary battery corresponds to the required charge amount maintenance section, the control unit calculates an amount of discharging power of the secondary battery using the electrical characteristic value of the secondary battery measured by the sensing unit during discharging of the secondary battery, and outputs a control signal for charging the secondary battery by an amount of charging power obtained as a result of adding an amount of power compensation to the calculated amount of discharging power when charging the secondary battery. a sensing unit to measure an electrical characteristic value of the secondary battery; a memory unit to store a charged power amount decrease section and a charged power amount increase section based on the electrical characteristic value of the secondary battery; and a control unit to output a control signal for reducing an amount of power charged in the secondary battery when a state of the secondary battery corresponds to the charged power amount decrease section based on the electrical characteristic value measured by the sensing unit, and to output a control signal for increasing an amount of power charged in the secondary battery when the state of the secondary battery corresponds to the charged power amount increase section based on the electrical characteristic value measured by the sensing unit, wherein the charged power amount decrease section is a section where the amount of power charged in the secondary battery is beyond a required charge amount maintenance section, the charged power amount increase section is a section where the amount of power charged in the secondary battery is below the required charge amount maintenance section, and wherein when the state of the secondary battery corresponds to the required charge amount maintenance section, the control unit calculates an amount of discharging power of the secondary battery using the electrical characteristic value of the secondary battery measured by the sensing unit during discharging of the secondary battery, and outputs a control signal for charging the secondary battery by an amount of charging power obtained as a result of adding an amount of power compensation to the calculated amount of discharging power when charging the secondary battery.