Abstract: This invention relates to a cleaning agent for a semi-conductor substrate, particularly, one having copper wirings on its surface, comprising a nonionic surfactant and a method for cleaning the same. The said cleaning agent and the method have made it possible to control a speed of etching on silicone oxide so as to remove impurities adsorbed on copper wirings and silicone oxide on a surface of a semi-conductor substrate having copper wirings on its surface, such as copper oxides and particles, without causing corrosion or oxidation of copper wirings nor causing roughness on the surface.