A steel for shaft, which has corrosion resistance, machinability, and straightness at substantially the same levels as those of free cutting steel 12L14 plated with Ni, which has conventionally been used as a steel for shaft, and need not be plated on its surfaces, thus making it possible to reduce the production cost therefor, and which comprises: 0.05% by mass or less of C; 0.15% by mass or less of Si; 0.40% by mass or less of Mn; 6.0 to 10.0% by mass of Cr; 0.10% by mass or less of S; 0.30 to 0.80% by mass of Ni; 0.10 to 0.30% by mass of Pb; 0.001 to 0.10% by mass of N; and the balance of Fe and an unavoidable impurity; and a steel shaft composed of said steel.