Provided are a flexible secondary battery and a method of manufacturing the same. The method includes forming an electrode including a metal fiber-like current collector and an active material combined with the metal fiber-like current collector; and providing a liquid pre-electrolyte that may be either thermally polymerized or crosslinked to the electrode and applying heat thereto, such that the liquid pre-electrolyte is integrated with the electrode and forms a gelated or solidified polymer electrode.