PURPOSE: To produce an antioxidant capable of controlling the oxidative stress in the living body, excellent in stability and useful for a food, etc., by grounding a plant containing cyanidin glycoside, defatting the ground material, extracting it with a solvent and subsequently concentrating the extract under a reduced pressure.

CONSTITUTION: This antioxidant is produced by grinding a plant containing cyanidin-3-O-(β)-glucoside of the formula, e.g. a black-kerneled rice, a red- kerneled rice, a black soybean or a blueberry, defatting the ground material, subsequently filtering it, extracting the resultant residue with a solvent such as 0.5% trifluoroacetic acid-95% ethanol solution and concentrating it under a reduced pressure.