The present invention relates to a nucleic acid inducing RNA interference and a use thereof, and more specifically, to a nucleic acid inducing RNA interference, modified by replacing, by a spacer capable of no base pairing, 5' terminal and 3' terminal regions in at least one single strand of the double strand of the nucleic acid inducing RNA interference. The nucleic acid inducing RNA interference of the present invention can provide: a nucleic acid having a novel modified form for preventing an off-target effect generated when inhibiting the expression of a target gene by an RNA interference phenomenon； and a method for selectively inhibiting the expression of a target gene by using the same. In addition, the nucleic acid inducing RNA interference according to the present invention solves the inaccuracy and side effects due to off-target, which are the problems of a known nucleic acid inducing RNA interference, by providing a nucleic acid inducing RNA interference as a novel modified form having target selectivity and specificity by preventing an off-target effect while inhibiting the expression of a target gene, and thus can be used, without worries, in the research of a technique for inhibiting the expression of a gene and in gene therapy.La presente invención se refiere a un ácido nucleico que induce ARN de interferencia y al uso del mismo, y más especialmente a un ácido nucleico que induce ARN de interferencia que comprende al menos una única cadena de cadenas dobles, la al menos una única cadena comprende una modificación sustituida en un espaciador, que es incapaz de formar un par de bases en la región del extremo 5´ o del extremo 3´； el ácido nucleico que induce ARN de interferencia de la presente invención es una forma modificada novedosa de nucleótido proporcionada para prevenir efectos de falla en alcanzar el objetivo, ofreciendo un método para reprimir selectivamente la expresión del gen objetivo； además, según la presente invención, el ácido nucleico qu
