The present invention relates to a novel, RNAi-inducing nucleic acid molecule having cell penetrating ability and the use thereof, and more particularly, to a novel, RNAi-inducing double-stranded nucleic acid molecule, which has a replacement of the phosphate backbone of at least one nucleotide with phosphorothioate or phosphorodithioate, and has a lipophilic compound conjugated thereto, and thus has high target gene-silencing efficiency while having the ability to penetrate cells without needing a separate intracellular delivery vehicle, and to a method of silencing a target gene using the nucleic acid molecule. The nucleic acid structure according to the present invention has both cholesterol modification and phosphorothioate modification introduced therein, and thus has high gene silencing efficiency while having the ability to penetrate cells without needing a separate intracellular delivery vehicle. Thus, it can be delivered into an actual target area in an amount sufficient for induction of RNAi, and thus can overcome the in vivo delivery problem occurring in the prior art. Therefore, the nucleic acid molecule according to the invention can effectively substitute for conventional siRNA molecules to treat cancer or viral infections.
