The present invention relates to fatty acid elongation promoting activity and polynucleotides encoding same, and the like. The present invention provides: polynucleotides comprising a base sequence set forth in SEQ ID NO:1 or SEQ ID NO:4; polynucleotides encoding proteins comprising the amino acid sequence set forth in SEQ ID NO:2; expression vectors and transformants which comprise these polynucleotides; a preparation method for lipids or fatty acids which uses said transformants; and food products, or the like, comprising the lipids or fatty acids prepared by such a preparation method.