To efficiently obtain the subject compound useful for coloring-agents, nutritive value-improving agents, feeds, etc., by reacting an enzyme solution obtained by extracting microorganisms having genes for biosynthesis of a carotenoid in a buffer solution containing an organic solvent solution of the carotenoid and cholic acid.

In producing a carotenoid by reacting an enzyme solution obtained by extracting microorganism having genes for biosynthesis of the carotenoid with the carotenoid to be a substrate and harvesting the carotenoid (e.g. astaxanthin, etc.), the useful carotenoid for natural coloring agents, nutritive value-improving agents for preventing cancers, feeds, etc., is obtained by dissolving the carotenoid to be the substrate in chloroform, ethanol or ethyl acetate, etc., bringing a final concentration of chloroform, ethanol or ethyl acetate, etc., to 0.6-5%, reacting the enzyme solution with the carotenoid to be the substrate in a buffer solution containing cholic acid, deoxycholic acid or CHAPS and bringing the final concentration of cholic acid, deoxycholic acid or CHAPS to 0.01-1%.