Provided are an austenitic heat resistant alloy capable of exhibiting sufficient molten-salt corrosion resistance even when exposed to a molten salt of 600° C. and a production method thereof, and an austenitic heat-resistant alloy material. An austenitic heat resistant alloy includes a base metal, and a Ni—Fe oxide having a spinel structure on or above the surface of the base metal. The base metal has a chemical composition consisting of, in mass %, C: 0.030 to 0.120%, Si: 0.02 to 1.00%, Mn: 0.10 to 2.00%, Cr: 20.0% or more to less than 28.0%, Ni: more than 35.0% to 50.0% or less, W: 4.0 to 10.0%, Ti: 0.01 to 0.30%, Nb: 0.01 to 1.00%, sol. Al: 0.0005 to 0.0400%, B: 0.0005 to 0.0100%, Mo: less than 0.5%, Co: 0 to 0.80%, and Cu: 0 to 0.50%, with the balance being Fe and impurities.