<;P>;PROBLEM TO BE SOLVED: To provide a masking agent capable of masking with the addition of an extremely small amount, rough taste of food and drink and drug, and flavor too strong as flavor of food and drink and drug, without changing the basic flavor balance of food and drink and drug, and to provide a masking method. <;P>;SOLUTION: This masking agent contains as the active ingredient, milk serum mineral which satisfies all conditions (a), (b) (c) (d) and (e) as follows: (a) ash content in the solid content of milk serum mineral is 25-75 mass%; (b) calcium content in the solid content of milk serum mineral is <;2 mass%; (c) calcium content in the ash content of milk serum mineral is <;5 mass%; (d) lactate content in the solid content of milk serum mineral is 1.0 mass% or above; and (e) the pH of 0.1 mass% aqueous solution of the solid content of milk serum mineral is 6.0-7.5. <;P>;COPYRIGHT: (C)2008,JPO&INPIT