A soft magnetic iron alloy sheet has a saturation magnetic flux density comparable to that of Permendur, with the same iron loss as electromagnetic pure iron, and a lower cost than Permendur. The soft magnetic iron alloy sheet includes, as a chemical composition, 30 at % or less of Co, 0.1 at % or more and 11 at % or less of N, and 1.2 at % or less of vanadium, with the remainder being Fe and impurities. In a thickness direction of the soft magnetic iron alloy sheet, a surface layer region has an average nitrogen concentration of 1 at % or more and 15 at % or less and an internal region has a lower average nitrogen concentration than the surface layer region. In the surface layer region, a thickness is 1% or more and 30% or less from both main surfaces of the sheet and iron-nitride martensite having a tetragonal structure is formed.