A Ti-Al-base alloy having excellent oxidation resistance, which comprises a base material and a surface portion provided on the surface of the base material, the surface portion comprising at least one member selected among Cr, Nb, Ta and W and capable of forming a dense film of an oxide of the above element or Al2O3 in a high-temperature oxidizing atmosphere; and a process for preparing at Ti-Al-based alloy having excellent oxidation resistance, which comprises heat-treating a Ti-Al-based alloy material having an Al content of 15 to 55 at% together with an oxide having a smaller negative value in standard free energy of formation than alumina. The Ti-Al-based alloy thus prepared has markedly improved oxidation and heat resistances even at a temperature as high as 900 DEG C or above and hence can be utilized as the materials of an automobile turbocharger, a gas turbine for power generation, a jet engine, and the like.