A secondary battery and a method for manufacturing the same are provided. An electrode assembly accommodated in the secondary battery having various shapes is manufactured. In particular, a method for manufacturing a secondary battery includes an electrode stack preparation step of preparing an electrode stack which includes a first unit cell having a first area and a second unit cell having a second area that is less than the first area, and which has a structure in which the second unit cell is disposed on one surface of the first unit cell. The method further includes a curved surface formation step of pressing at least a part of an independent portion, which does not overlap the second unit cell, of the first unit cell to form a curved surface on the at least the part of the independent portion.