An object of the present invention is to provide a copper foil inexpensive and sufficient in tensile strength even after heat treatment. The copper foil includes zinc in a content range of 0.02% by mass to 2.7% by mass in the total mass of the entire copper foil, and if the regions in thicknesses direction from both surfaces of the copper foil where occupies 5% by mass in the total mass of the entire copper foil are referred to as the respective external layers and a region between one external layer and the other external layer is referred to as an internal layer, the internal layer includes copper as a main element and includes 100 ppm or more of one or mixture of small amount-elements selected from carbon, sulfur, chlorine and nitrogen, and includes zinc at 10% or more in the total mass of zinc included in the entire copper foil.