A method for manufacturing a secondary battery , the method comprising: an electrode assembly preparation step of preparing an electrode assembly which has a structure, in which electrodes and separators are alternately disposed, and on which flat top and bottom surfaces are formed; a first pressing step of pressing the top and bottom surfaces of the electrode assembly by using a first pressing device, on which a curved surface (C) is formed, to form a curved surface (C), which has a shape corresponding to that of the curved surface (C) formed on the first pressing device, on each of the top and bottom surfaces of the electrode assembly ; an accommodation step of accommodating the electrode assembly , on which the curved surface (C) is formed, in a pouch type exterior in which a cup having a concave shape is formed; a second pressing step of pressing the curved surface (C), which is formed on the electrode assembly in the first pressing step, and an outer surface of the pouch type exterior by using a second pressing device on which a curved surface is formed, a surface leveling step which is performed after the second pressing step and in which the curved surface formed on the exterior, which is formed in the second pressing step, is leveled, and a third pressing step of additionally pressing the curved surface (C) formed on the electrode assembly and the curved surface formed on the exterior, which are formed in the second pressing step, by using a third pressing device on which a curved surface (C) is formed, wherein, in the surface leveling step, a roller having a cylindrical shape rotates on the curved surface formed on the exterior to improve evenness of the curved surface formed on the exterior, and wherein the third pressing step is performed after the surface leveling step. an electrode assembly preparation step of preparing an electrode assembly which has a structure, in which electrodes and separators are alternately disposed, and on which flat top and bottom surfaces are formed; a first pressing step of pressing the top and bottom surfaces of the electrode assembly by using a first pressing device, on which a curved surface (C) is formed, to form a curved surface (C), which has a shape corresponding to that of the curved surface (C) formed on the first pressing device, on each of the top and bottom surfaces of the electrode assembly ; an accommodation step of accommodating the electrode assembly , on which the curved surface (C) is formed, in a pouch type exterior in which a cup having a concave shape is formed; a second pressing step of pressing the curved surface (C), which is formed on the electrode assembly in the first pressing step, and an outer surface of the pouch type exterior by using a second pressing device on which a curved surface is formed, a surface leveling step which is performed after the second pressing step and in which the curved surface formed on the exterior, which is formed in the second pressing step, is leveled, and a third pressing step of additionally pressing the curved surface (C) formed on the electrode assembly and the curved surface formed on the exterior, which are formed in the second pressing step, by using a third pressing device on which a curved surface (C) is formed, wherein, in the surface leveling step, a roller having a cylindrical shape rotates on the curved surface formed on the exterior to improve evenness of the curved surface formed on the exterior, and wherein the third pressing step is performed after the surface leveling step. <EOS>