This invention provides an effective means for inhibiting the growth of microorganisms in a concentrate-type milk-based acidic beverage that contains milk after a package is opened. The concentrate-type milk-based acidic beverage of the invention comprises (A) milk, (B) µ-polylysine, and (C) at least one member selected from among benzoic acid, p-hydroxybenzoic acid esters, and a salt of either thereof, wherein the milk solids-non-fat content is 1.5% to 4.5% by weight, and the Brix value is 40 to 60.
