A secondary battery may include a plurality of cathode layers which have a porous structure including a plurality of pores, have a flat plate-shape, and are arranged to be spaced apart from each other in a direction. The secondary battery further includes an electrolyte layer including a first electrolyte film and a second electrolyte film, where the first electrolyte film surrounds external surfaces of the cathode layers, and the second electrolyte film is disposed in the pores of the cathode layers. The secondary battery further includes an anode layer surrounding the first electrolyte film.