PROBLEM TO BE SOLVED: To provide an antioxidative substance and a cosmetic that exhibit an unprecedentedly highly antioxidative effect to suppress damages of a cell caused by ultraviolet rays and therefore is useful for suppressing wrinkles/spots caused by photoageing by ultraviolet irradiation.SOLUTION: An extract liquid of a purple sweet potato is added to a nutrient medium usually used for cultivation of a bacterium. Saccharomyces cerevisiae is cultivated and, after the cultivation is finished, a bacterial cell is separated from the culture solution. The use of an extraction liquid of the cultured bacterial cell as an effective ingredient permits acquisition of the antioxidant, the ultraviolet hazard inhibitor and the anti-photoageing cosmetic, each being excellent.
