It is intended to provide methods for suppressing the huntingtin gene expression by using a double-stranded RNA (dsRNA), huntingtin gene expression inhibitors to suppress the huntingtin gene expression, and preventives and/or remedies of Huntington's disease. Targeting against a specific sequence of mRNA at immediately upstream of CAG repeats in HD genes of Huntington's disease, the huntingtin gene expression is suppressed by using a dsRNA homologous to the sequence. In this invention, a short siRNA (short double-stranded RNA) having bp as short as around 21-23 bp can be effectively used as the dsRNA homologous to a specific RNA sequence in a region at immediately upstream of CAG repeats. The dsRNA of this present invention can be used as a huntingtin gene expression inhibitor, or a preventive and/or a remedy of Huntington's disease by administering or introducing into a living body or a living cell in mammals for the prevention and/or treatment of Huntington's disease.