Disclosed is single-stranded cyclic RNA having a sustained or extended RNA interferenceactivity. The single-stranded cyclic RNA comprises a sense strand sequence,an antisense strand sequence complementary to the sense strand sequence, andtwo loop sequences which are the same as or different from each other and are locatedbetween the sense strand and the antisense strand so as to bind the both strandsto each other, wherein the sense strand and the antisense strand are paired toform a stem.
