The effect of Cu on the hot workability of austenitic stainless steel has been investigated by performing tensile tests and examination by scanning electron microscopy and Auger electron spectroscopy. Reduction of area decreased linearly with increasing Cu contents at deformation temperature above 1100℃. But, at the deformation temperature below 1100℃, the effect of Cu on reduction of area changed drastically at about 3.2% Cu. At lower Cu contents, reduction of area decreased in the same manner with that observed above 1100℃. However, as Cu contents exceeded about 3.2%, reduction of area rapidly decreased with increasing Cu contents. Fracture mode changed from ductile rupture to intergranular decohesion as Cu contents increased in the ductility trough. The occurrence of embrittlement would be attributed to the segregation of Cu and S at austenite grain boundary.