We paid attention to stearoyl-CoA desaturase gene, and investigated the relation between this gene and the unsaturated fatty acid content in beef fat. As a result, we found that the unsaturated fatty acid content was associated with the genotype of this gene, classified according to several single nucleotide polymorphisms (SNPs) on this gene. The present invention is a method to predict the unsaturated fatty acid content in beef (or milk) fat, on the basis of the genotype of bovine stearoyl-CoA desaturase, and useful prediction method for beef quality such as taste and texture.