A Ti--Al system intermetallic compound comprised of 25 at. % to 75 at. % of aluminum and the remainder of titanium. The compound includes 0.004 at. % to 1.0 at. % each of at least one halogen element selected from the group consisting of fluorine, chlorine, bromine and iodine. Alternatively, to provide a Ti--Al system intermetallic compound with oxidation resistance, the surface of the Ti--Al system intermetallic compound is heated to 800.degree. C. to 1125.degree. C. in a mixture of gas including 2 ppm to 1% by volume of at least one halogen element selected from the group consisting of fluorine, chlorine, bromine and iodine, and also including 0.1% by volume or more of oxygen. Thus, a dense aluminum oxide film is formed on the surface of the intermetallic compound. Alternatively, to form the dense aluminum oxide film, at least one halogen element is first disposed on the part providing the oxidation resistance of the intermetallic compound, and heated for 0.2 hour or longer at 800.degree. C. to 1125.degree. C. In this case, the halogen amount should be between 0.002 mol/m.sup.2 and 2 mol/m.sup.2.