Cu-Cu2O eutectic bonding of copper to alumina has been studied at 1075-degrees-C in nitrogen gas, In order to elucidate the reaction at the Cu/Al2O3 interface, the bonding time was prolonged up to 24 h at 1075-degrees-C in nitrogen gas. CuAlO2 was found at the Cu/Al2O3 interface, and it seems that CuAlO2 was formed even with a short bonding time. CuAlO2 enhanced the bonding strength. There seem to be two kinds of bonding mechanism working at the Cu/Al2O3 interface.