Disclosed herein is an electrode assembly including two or more unit cells, each of which includes a cathode, an anode, and a separator disposed between the cathode and the anode, electrode tabs protruding from the respective electrodes, wherein the unit cells are stacked in a height direction on the basis of a plane, at least two of the unit cells having different planer sizes, and one or more corners of each of the unit cells, which do not tangent to one side of each of the unit cells at which the electrode tabs are formed, are round.