Since the Cu content in steel causes hot shortness, it is important to understand the behavior of Cu during high-temperature oxidation in order to control the precipitated Cu. This study examined Cu distribution during the oxidation of steel. The oxidation tests revealed that precipitated Cu existing in the scale/steel interface was absorbed into the Fe₃O₄ layer or evaporated into the atmosphere as Cu. Then, a method proposed to suppress hot shortness was tested by oxidation-tensile tests at high temperature and the method was proven to be effective.