To achieve straightening in an in-line process by heating to a warm working region temp. before wire drawing and after cutting/before bend- straightening when producing a straight bar of austenitic heat resisting steel SUH35 material having hard workability so as to improve a straightening efficiency.

Before a wire rod is drawn to a prescribed diameter wire rod, the wire rod is heated to the warm working temp. region. Further, after drawing, a bar stock cut to a prescribed length is cooled to a normal temp. or a temp. near normal temp., again the bar is heated to the warm temp. region by induction heating, hardness, in particular, surface hardness is lowered and then by using its residual heat and executing bend straightening, the straight bar having high straightness is produced. Further, the warm working region temp. is preferably 1100±50°C and a straightening machine used for straightening is preferably polishing straightening machine.