To produce a remarkably good corrosion resistant zirconium based alloy used as a nuclear structural material such as a fuel sheath material, a lattice and an introduction pipe.

This corrosion resistant zirconium based alloy for the nuclear furl sheath material is produced from a low-tin zirconium alloy having a composition containing, by weight, 0.60 to 2.0% Nb and 0.50% Fe in the case of 0.25% Sn, 0.35 to 0.50% Fe in the case of 0.40% Sn, 0.25 to 0.50% Fe in the case of 0.50% Sn, 0.05 to 0.50% Fe in the case of 0.70% Sn or 0.05 to 0.50% Fe in the case of 1.0% Sn (as shown in the region 10 in the figure 1), wherein (Sn+Fe)% is ≥0.75, and containing the other componential elements of ≤0.50%, and the balance essentially Zr.