An apparatus configured to estimate SOH (State Of Health) of a battery based on a battery voltage variation pattern, comprising: a data storing unit configured to obtain and store battery voltage, current and temperature data from a voltage sensing unit, a current sensing unit and a temperature sensing unit, which are coupled to a battery, whenever SOH is estimated; a first SOC (State Of Charge) estimating unit configured to estimate a first SOC by an Ampere counting manner using the stored battery current data; a second SOC estimating unit configured to calculate and store a second SOC corresponding to the estimated open-circuit voltage and the battery temperature using predetermined correlations between the open-circuit voltage and the SOC and between the battery temperature and the SOC, the open-circuit voltage being estimated using measured battery voltage and an experimentally obtained voltage variation operation function mapping a battery voltage variation into an open-circuit voltage variation; a weighted mean convergence calculating unit configured to calculate and store a convergence value for a weighted mean value of a ratio of a variation of the second SOC to a variation of the first SOC by repeatedly calculating weighted mean value of said ratio by means of a weighted mean arithmetic progression; and a SOH estimating unit configured to estimate a battery capacity corresponding to the stored weighted mean convergence value of the SOC variation ratio by using a look-up table with predetermined correlations defining a battery capacity for each weighted mean convergence value of SOC variation ratio, estimate a relative ratio of the estimated battery capacity to an initial battery capacity, and storing the relative ratio as SOH. a data storing unit configured to obtain and store battery voltage, current and temperature data from a voltage sensing unit, a current sensing unit and a temperature sensing unit, which are coupled to a battery, whenever SOH is estimated; a first SOC (State Of Charge) estimating unit configured to estimate a first SOC by an Ampere counting manner using the stored battery current data; a second SOC estimating unit configured to calculate and store a second SOC corresponding to the estimated open-circuit voltage and the battery temperature using predetermined correlations between the open-circuit voltage and the SOC and between the battery temperature and the SOC, the open-circuit voltage being estimated using measured battery voltage and an experimentally obtained voltage variation operation function mapping a battery voltage variation into an open-circuit voltage variation; a weighted mean convergence calculating unit configured to calculate and store a convergence value for a weighted mean value of a ratio of a variation of the second SOC to a variation of the first SOC by repeatedly calculating weighted mean value of said ratio by means of a weighted mean arithmetic progression; and a SOH estimating unit configured to estimate a battery capacity corresponding to the stored weighted mean convergence value of the SOC variation ratio by using a look-up table with predetermined correlations defining a battery capacity for each weighted mean convergence value of SOC variation ratio, estimate a relative ratio of the estimated battery capacity to an initial battery capacity, and storing the relative ratio as SOH.