An aluminum-alloy foil that enables to satisfy both of high elongation and high strength even in the case of reducing the foil thickness. The chemical composition of the aluminum-alloy foil contains, in mass %, Fe: 1.0% or more and 2.0% or less, Cu: 0.1% or more and 0.5% or less, and Mn: 0.05% or less, the remainder being Al and unavoidable impurities. The aluminum-alloy foil has a foil thickness of 20 μm or less, and satisfies the relation El≥100×t/UTS. Here, t represents a foil thickness (μm), UTS represents a tensile strength (MPa), and El represents an elongation (%).