PURPOSE: To facilitate treatment of carbon fiber so as to provide a secondary battery without exerting an adverse effect on an electric discharging capacity by containing the carbon fiber as an electrode active material inside a cylindrical or bag-like separator.

CONSTITUTION: Carbon fiber is an electrode active material is contained inside a cylindrical or bag-like separator, thus forming an electrode. PAN carbon fiber, e.g. is developed on the separator consisting of a polypropylene porous film. The separator is formed into a cylindrical shape by the use of a sealer. The carbon fiber is contained inside the separator, thereby constituting an operating electrode. Transient metal oxide is used as a positive electrode on the opposite side and a non-aqueous electrolyte having lithium salt dissolved in a non-aqueous solvent is used as an electrolyte in the case where the operating electrode serves as a negative electrode of a high voltage battery. Consequently, it is possible to facilitate treatment of the carbon fiber, which has been difficult to be treated as the electrode active material, and to provide a secondary battery without exerting an adverse effect on an electric discharging capacity.