PROBLEM TO BE SOLVED: To provide a material which has effects of improving flavor and taste, with unpleasant odor, e.g. processing odor, masked without impairing the original natural flavor of an additive by adding the material to a flavor formulation and then adding the formulation to a food and drink, e.g. drinks, jelly, etc.SOLUTION: A flavor taste improver for foods and drinks is obtained by charging a citrus fruit or a material originated from a citrus fruit in a tank 110 as a raw material, evacuating the tank 110 by a pressure reducing device 120, introducing microwaves generated by a microwave generator 130 into the raw material through a microwave waveguide 113, conducting an extraction treatment while irradiating with the microwaves and blending the extract obtained by the pressure reduction microwave irradiation extraction treatment with a food and drink. The extract obtained may be blended, in an adequate amount, with an essential oil or a water extract obtained by existing techniques, including wa
