The influence of iron content on mechanical properties of Al–1.0mass%Si–0.5mass%Mg–0.1mass%Mn alloy T4 sheets was investigated. The amount of Al–Fe–Si second phase particles increased with iron content, thus silicon atoms were consumed by formation of Al–Fe–Si particles. Furthermore, tensile strength of the samples in T4 condition was not influenced by iron content, but the paint bake response decreased over 0.5 mass%. This was the result of lowering age hardening rate at the early stage of artificial aging because of the loss of silicon atoms. Also, bendability of the samples became worse with iron content. But, it was the worst at 0.5 mass% of iron content, while it at over 0.5 mass% became better or the same. The reason was considered as below. Cracking by bending occurred along the second phase particles and the shear bands. And the amount of second phase particles increased with iron content, whereas the formation of shear bands decreased with iron content over 0.5 mass% because of the loss of silicon. In addition, formability became worse slightly with iron content.