A cell balancing apparatus using a voltage variation pattern of a battery cell, configured to balance state of charge SOC of a plurality of cells (C1...Cm) in a battery, the apparatus comprising: an open circuit voltage OCV estimating means for measuring voltage of each cell in the battery and estimating OCV of each cell using a voltage variation pattern of each cell defined by three output voltages Vn; Vn-1 and Vn-2; and a cell balancing unit for balancing SOC of each cell by selecting a target cell for balancing through comparison of the estimated OCV of each cell and controlling a balancing circuit (B1...Bm) corresponding to the selected cell, wherein the OCV estimating means comprises: a voltage measuring unit for measuring voltage of each cell; a temperature measuring unit for measuring temperature of each cell; a data storing unit for periodically receiving the voltage and temperature of each cell from the voltage measuring unit and the temperature measuring unit and storing the voltage and temperature in a memory unit; an OCV variation estimating unit for estimating a present OCV variation of each cell by calculating an OCV variation of each cell ΔOCVn(k) from the voltage variation pattern defined by three output voltages Vn; Vn-1 and Vn-2, stored in the memory unit, using a mathematical model that defines a correlation between the output voltage variation pattern and the OCV variation, and reflecting a correction factor F corresponding to the temperature of each cell on the calculated OCV variation of each cell; and an OCV estimating unit for estimating a present OCV of each cell by reflecting the calculated OCV variation of each cell on a previous OCV of each cell, wherein Δ ⁢ OCV n k = OCV n k - OCV n - 1 k = G V × F T = V n - V n - 1 × g ⁢ V n V n - 1 V n - 2 × F T wherein g(V n, V n-1, V n-2) is a relative ratio of a previous output voltage variation to a present output voltage variation: |V n-1 -V n-2 | / |V n -V n-1 | wherein "n" is an order index of estimating an OCV variation, and "k" is an order index of a cell. an open circuit voltage OCV estimating means for measuring voltage of each cell in the battery and estimating OCV of each cell using a voltage variation pattern of each cell defined by three output voltages Vn; Vn-1 and Vn-2; and a cell balancing unit for balancing SOC of each cell by selecting a target cell for balancing through comparison of the estimated OCV of each cell and controlling a balancing circuit (B1...Bm) corresponding to the selected cell, wherein the OCV estimating means comprises: a voltage measuring unit for measuring voltage of each cell; a temperature measuring unit for measuring temperature of each cell; a data storing unit for periodically receiving the voltage and temperature of each cell from the voltage measuring unit and the temperature measuring unit and storing the voltage and temperature in a memory unit; an OCV variation estimating unit for estimating a present OCV variation of each cell by calculating an OCV variation of each cell ΔOCVn(k) from the voltage variation pattern defined by three output voltages Vn; Vn-1 and Vn-2, stored in the memory unit, using a mathematical model that defines a correlation between the output voltage variation pattern and the OCV variation, and reflecting a correction factor F corresponding to the temperature of each cell on the calculated OCV variation of each cell; and an OCV estimating unit for estimating a present OCV of each cell by reflecting the calculated OCV variation of each cell on a previous OCV of each cell, wherein Δ ⁢ OCV n k = OCV n k - OCV n - 1 k = G V × F T = V n - V n - 1 × g ⁢ V n V n - 1 V n - 2 × F T wherein g(V n, V n-1, V n-2) is a relative ratio of a previous output voltage variation to a present output voltage variation: |V n-1 -V n-2 | / |V n -V n-1 | wherein "n" is an order index of estimating an OCV variation, and "k" is an order index of a cell.