A liquid for polishing a metal is provided that is used for chemically and mechanically polishing a conductor film including copper or a copper alloy in production of a semiconductor device, and a polishing method using the metal-polishing liquid is also provided. The liquid includes: (a) colloidal silica particles having an average primary particle size of from 10 nm to 25 nm and an average secondary particle size of from 50 nm to 70 nm; (b) a metal anticorrosive agent; (c) at least one compound selected from the group consisting of a surfactant and a water-soluble polymer compound; (d) an oxidizing agent; and (e) an organic acid.