To realize high capacity of a battery by firmly adhering an active material layer and a foil main body in making a needle-like body bite inside the active material layer formed on a surface of the foil main body, by protrusively forming the needle-like body from a foil surface at specific average density.

Surface-treated copper foil is formed on a foil surface by projecting a needle-like body 11 from a surface of a foil main body 10 in average density of 5 to 900 pieces/μm2. A thickness of the foil main body 10 is set to about 5 to 100 μm, preferably 10 to 30 μm. The needle-like body 11 is formed on the foil surface having the needle-like body 11 of copper oxide grown from the foil main body 10 by performing oxidizing processing on the copper foil in the first place. An oxidizing processing method is performed by heating it or soaking it in alkali containing an oxidizing agent such as chlorite and peroxodisulfate or a neutral aqueous solution. The needle-like body 11 composed of copper is formed by reducing copper oxide of the needle-like body 11 which is formed on a surface of the copper foil by performing electrolytic processing using the oxidizing processing performed copper foil as a cathode.