Provided is a method for producing an unsaturated fatty acid oxide (e.g. ω3 fatty acid oxide) that is new and has more beneficial features compared to conventional technologies. This method uses a lipoxygenase-containing composition (e.g. a lipoxygenase-containing composition derived from beans) as a lipoxygenase enzyme, and also uses a freezing method with organic solvent extraction. The present invention makes it possible to produce an unsaturated fatty acid oxide (e.g. ω3 fatty acid oxide) efficiently and at a low cost. The present invention also provides a pharmaceutical composition containing an ω3 fatty acid oxide isolated and purified by this method as an active ingredient.
