A polishing agent for copper polishing, comprising (A) an inorganic acid with divalent or greater valence, (B) an amino acid, (C) a protective film-forming agent, (D) an abrasive, (E) an oxidizing agent and (F) water, wherein the content of the component (A) is at least 0.08 mol/kg, the content of the component (B) is at least 0.20 mol/kg, the content of the component (C) is at least 0.02 mol/kg, and either or both of the following conditions (i) and (ii) are satisfied. (i): The proportion of the content of the component (A) with respect to the content of the component (C) is 2.00 or greater. (ii): It further comprises (G) at least one kind selected from among organic acids and their acid anhydrides.