There is provided a metal foil suitable for an electrode substrate for an electronic element, which makes it possible to suppress oxidation of the ultra-smooth surface and also prevent roll scratches when wound in a roll. The metal foil of the present invention is made of copper or copper alloy. The front surface of the metal foil has an ultra-smooth surface profile having an arithmetic mean roughness Ra of 30 nm or less as determined in accordance with JIS B 0601-2001. The back surface of the metal has a concave-dominant surface profile having a Pv/Pp ratio of 1.5 or more, the Pv/Pp ratio being a ratio of a maximum profile valley depth Pv to a maximum profile peak height Pp of a profile curve as determined in a rectangular area of 181 μm by 136 μm in accordance with JIS B 0601-2001.