To provide a method for producing, at high purity, a recombinant baculovirus which exhibits intended immunogenicity and is useful for a pharmaceutical (e.g., a vaccine), a transfer vector for use in the production of the recombinant baculovirus, and a method for producing the transfer vector. The method for producing a transfer vector which includes therein a fusion gene containing at least one gene encoding a virus-particle-forming protein and a gene encoding a foreign immunogenic protein, the method including modifying the polynucleotide sequence of the gene encoding the virus-particle-forming protein so as not to alter the amino acid residues constituting a corresponding naturally occurring virus-particle-forming protein and/or modifying the polynucleotide sequence of the gene so that a portion of the amino acid residues constituting the naturally occurring virus-particle-forming protein is deleted.
