1. An apparatus for estimating SOH (State Of Health) of a battery based on a battery voltage variation pattern, comprising: a first SOC (State Of Charge) estimating unit for estimating a first SOC by using a battery current data obtained at time intervals; a second SOC estimating unit for estimating an open-circuit voltage from a battery voltage behavior defined by variation patterns of battery voltages obtained at time intervals, and calculating and storing a second SOC corresponding to the estimated open-circuit voltage and the battery temperature using predetermined correlations allowing calculation of SOC from the open-circuit voltage and the battery temperature; a weighted mean convergence calculating unit for calculating a convergence value for a weighted mean value of a relative ratio (or, a SOC variation ratio) between a variation of the first SOC and a variation of the second SOC; and a SOH estimating unit for estimating a battery capacity corresponding to the stored weighted mean convergence value by using a predetermined correlation allowing calculation of the battery capacity from the weighted mean convergence value, estimating SOH by using the estimated battery capacity, and storing the estimated SOH.