Disclosed is a method for manufacturing a secondary battery. More specifically, the present disclosure relates to a method for manufacturing an electrode assembly by stacking a plurality of bi-cell type and/or monocell type unit cells.A method for manufacturing an electrode assembly according to the present disclosure can easily remove the curvature which occurs in a unit cell in a roll lamination process, and fabricate a flat plate electrode assembly with a simple process. Further, when the electrode assembly is manufactured with the method described above, the curvature between the unit cells constituting the electrode assembly may be offset, and accordingly, a time during which the flat plate shape in the electrode assembly is maintained may be extended significantly.