An austenitic Fe—Ni—Cr alloy comprises C: 0.005˜0.03 mass %, Si: 0.17˜1.0 mass %, Mn: not more than 2.0 mass %, P: not more than 0.030 mass %, S: not more than 0.0015 mass %, Cr: 18˜28 mass %, Ni: 21.5˜32 mass %, Mo: 0.10˜2.8 mass %, Co: 0.05˜2.0 mass %, Cu: less than 0.25 mass %, N: not more than 0.018 mass %, Al: 0.10˜1.0 mass %, Ti: 0.10˜1.0 mass %, Zr: 0.01˜0.5 mass %, and the balance being Fe and inevitable impurities; wherein Cr, Mo, N and Cu satisfy PRE=Cr+3.3×Mo+16×N≧20.0 and PREH=411-13.2×Cr-5.8×Mo+0.1×Mo2+1.2×Cu≦145.0 and wherein Al, Ti, and Zr satisfy 0.5≦Al+Ti+1.5×Zr≦1.5, and has an excellent corrosion resistance in air or under a wet environment even at a surface state having an oxide film formed by an intermediate heat treatment.