Abstract: The present invention relates to a method for producing and purifying SDA at high purity and/or high yield from a raw material such as anchovy oil. According to the present invention, when separating and purifying SDA from a raw material (e.g. anchovy oil) that includes SDA, high-quality, high-purity SDA is produced at a high recovery rate by using a combination of ethyl esterification and a silver nitrate treatment method. (1) A purification method selected from the group consisting of a thin-film vacuum superfractionation method, a simulated moving bed chromatography method, a urea addition method, and a molecular distillation method, and (2) an adsorbent treatment may be combined, as necessary.