The present invention relates to a double-stranded RNA molecule improved to control the gene expression suppressing effect of an siRNA. The double-stranded RNA molecule of the present invention is designed such that, in a double-stranded RNA molecule capable of suppressing the expression of a target gene in a cell by RNAi, one or more nucleotides in order from the 3"- or 5"-end of the sense strand of double-stranded part in said RNA molecule are not complementary to the antisense strand. Further, in the double-stranded RNA molecule of the present invention, the sense strand of the double-stranded part has adequate number of nucleotides which are complementary to the antisense strand for enabling the hybridization of both strands in the cell.
