A processing method for the metal surface in a dual damascene manufacturing is applied to a dual damascene semiconductor structure. The dual damascene semiconductor structure has a metal structure and a spin-on-dielectric (SOD) layer formed on the metal structure, wherein the SOD layer has at least one opening exposing a partial surface of the metal structure. Before the opening is filled, the monoxide on the exposed surface is first removed, then the exposed surface is treated by the plasma at an angle inclined to an axis perpendicular to the exposed surface. The processing method provided in the present invention can avoid the exposed surface being damaged by the plasma and improve the adhesion force between the exposed metal surface and the stuff.