Polishing agent for copper polishing and polishing method using the same

Provided is a polishing agent for copper polishing that includes: at least one leveling agent selected from the group consisting of tetrazole, tetrazole derivatives, triazole, and triazole derivatives (with the exception of benzotriazole and benzotriazole derivatives); inorganic acid; amino acid, protective film-forming agent; abrasive grains; oxidant; and water. The inorganic acid content is 0.080 mol/kg or greater, the amino acid content is 0.200 mol/kg or greater, the protective film-forming agent content is 0.020 mol/kg or greater, and the ratio of the inorganic acid to the protective film-forming agent content is 3.0 or greater.