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.