The present invention relates to a method for expressing and accumulating a low-molecular peptide in plant seeds; a vector therefore; and a plant transformed with the vector. In the present invention, an intended peptide composed of 3 to 40 amino acid residues is expressed and accumulated in seeds of a plant by transforming the plant with a fusion protein expression vector comprising a gene encoding a member of the glutelin multigene family and two or more copies of a gene encoding the intended peptide ligated downstream of the gene under the control of a promoter.