The present invention provides arachidonic acid-containing plants and soybeans, and a method of use thereof. The arachidonic acid-containing plant is produced by a process that includes an arachidonic acid producing step in which fatty acid synthetase genes associated with the biosynthesis of arachidonic acid are introduced into a plant to produce arachidonic acid. Thus, plants or soybeans containing arachidonic acid can easily be obtained. Therefore, it is possible to obtain a large amount of arachidonic acid at low cost.