The present invention relates to a polishing slurry including: a colloidal silica having an average particle size of 40 nm or more; water; and a ζ potential adjusting component, in which the ζ potential adjusting component includes at least one water-soluble organic polymer selected from a water-soluble polyether polyamine and a water-soluble polyalkylene polyamine and at least one acid selected from hydrochloric acid, sulfuric acid, nitric acid, nitrous acid and amidosulfuric acid, and the ζ potential adjusting component contains the acid at a ratio of from 0.6 to 1.4 to the water-soluble organic polymer in terms of molar ratio, and the polishing slurry has a pH of 8 or more.