A secondary battery has an electrode assembly including a negative electrode plate and a positive electrode plate and a battery case accommodating the electrode assembly. The negative electrode plate includes a negative electrode core body and first and second negative electrode active material mix layers disposed on the respective surfaces of the negative electrode core body. A first separator is bonded to the first negative electrode active material mix layer, and a second separator is bonded to the second negative electrode active material mix layer. In at least one side edge portion of the negative electrode plate, the first separator has a first bent portion bent toward the second separator, the negative electrode core body has a second bent portion bent toward the second separator, and the second negative electrode active material mix layer includes a region having a thickness less than the thickness of the central portion.