Abstract: The present invention aims at providing structural materials having a resistance to degradation by neutron irradiation, causing no SCC in an environment of light-water reactors even after subjecting the materials to neutron irradiation of approximately at least 1.times.10.sup.22 n/cm.sup.2 (E>1 MeV), and having thermal expansion coefficients approximately similar to that of structural materials. The high nickel austenitic stainless steels of the present invention having a resistance to degradation by neutron irradiation can be produced by subjecting stainless steels having compositions (by weight %) of 0.005 to 0.08% of carbon, at most 0.3% of Mn, at most 0.2% of (Si+P+S), 25 to 40% of Ni, 25 to 40% of Cr, at most 3% of Mo or at most 5% of (Mo+W), at most 0.3% of Nb+Ta, at most 0.3% of Ti, at most 0.001% of B and the balance of Fe to a solution-annealing treatment at a temperature of 1000 to 1150.degree. C.