At least one foil surface of an aluminum foil is roughened; and in arithmetic mean roughnesses Ra, stipulated in JIS B 0601:2001, of the roughened surface(s), A, which is the arithmetic mean roughness Ra measured in a direction at a right angle to a rolling direction during foil rolling, and B, which is the arithmetic mean roughness Ra measured in a direction parallel to the rolling direction during foil rolling, satisfy the following relationships: 0.15 μm≦A≦2.0 μm; 0.15 μm≦B≦2.0 μm; and 0.5≦B/A≦1.5. Preferably 50-1000 μg/m2 of oil is adhered to the roughened foil surface. The oil is preferably rolling oil.