Abstract: A high-purity reinforcing steel resistant to salt and capable of preventing deterioration of concrete substantially completely over a long period when the salt content of the concrete is not greater than 0.5 wt % in terms of Nacl amount in the sand of concrete. The reinforcing steel essentially consists of 0.001 to 1.0 wt % of C, less than 0.01 wt % of Si, 0.01 to 2.0 wt % of Mn, less than 0.015 wt % of P, less than 0.005 wt % of S, 0.01 to 0.5 wt % of Cu, 0.01 to 0.5 wt % of W, 0.001 to 0.10 wt % of Al and the balance Fe and incidental impurities. Disclosed also is another reinforcing steel capable of remarkably retarding deterioration of concrete even under such a severe corrosive condition that the salt content of the concrete exceeds 0.5 wt % in terms of Nacl amount in the same of concrete. This reinforcing steel essentially consists of 0.001 to 1.0 wt % of C, not greater than 0.05 wt % of Si, 0.01 to 2.0 wt % of Mn, less than 0.015 wt % of P, less than 0.005 wt % of S, 1.0 to 5.5 wt % of Ni, 0.001 to 0.