A double stranded RNA having a specific nucleotide sequence is useful for treating cellular proliferative disorders. The double stranded RNA acts as siRNA against the Rad51 gene. The double stranded RNA of the present invention inhibits cellular proliferation itself. In addition, co-administration of the double stranded RNA with a chemotherapeutic agent further enhances its pharmacological effect. The combined use of the double stranded RNA with an agent having a nucleic acid synthesis-inhibitory activity or a nucleic acid-impairing activity is particularly effective.