Disclosed is a method for forming a metal line. The method includes preparing a semiconductor substrate having a first metal line, performing an oxidation process with respect to the first metal line, performing an oxide removal process to remove an oxide generated in the oxidation process, forming an etch stop layer on the metal line, forming an interlayer dielectric layer on the first metal line, and forming a damascene pattern on the interlayer dielectric layer, and forming a second metal line, which is connected with the first metal line, in the damascene pattern. The oxidation process for the first metal line can include a hydrogen peroxide treatment process using a solution including oxygen. The oxide removal process can be performed by using an oxalic acid (HOOC—COOH) solution.