PROBLEM TO BE SOLVED: To provide a container-packed milk-containing beverage of which good flavor can be preserved in a stable state with suppression of off-flavor such as milk smell even under normal temperature for drinking little by little for a long time and a method for improving the flavor of a container-packed milk-containing beverage.SOLUTION: The container-packed milk-containing beverage includes milk protein (A) in an amount of 0.4 to 1.0 mass%, and polyphenol (B) in an amount of 0.04 to 0.1 mass%, with a pH of 5.4 or more and 6.3 or less. The method for manufacturing the same and the method for improving the flavor of a container-packed milk-containing beverage include adjusting an amount of milk protein (A) to 0.4 to 1.0 mass%, polyphenol (B) to 0.04 to 0.1 mass%, and adjusting the pH to 5.4 or more and 6.3 or less.
