Double-stranded RNA synthesized using native human DNA as template is found to be an excellent interferon inducer with low toxicity in spite of homologous native to host cell. It is produced by reacting ATP, GTP, CTP and UTP with one another in the presence of a native human DNA as template by the catalytic action of an active RNA polymerase to form RNA and subjecting the resulting RNA to annealing by heating it at a temperature of 70.degree. to 100.degree. C. and gradually cooling to room temperature or below to form double-stranded regions between their molecules.