The present disclosure is directed to an artificial mimic miRNA utilizing miRNA. An artificial mimic miRNA is a single-stranded nucleic acid including: a X region； and a Y region, the Y region and the X region being linked, wherein the X region is a guide strand sequence of a mature miRNA or a partial sequence of the guide strand sequence of the mature miRNA and consists of a linking side region (XB) and a non-linking side region (XF) to the Y region, the linking side region (XB) is a sequence that does not cause intramolecular annealing within its region, and the Y region is a sequence that intramolecularly anneals to the non-linking side region (XF) of the X region. According to the artificial mimic miRNA of the present invention, the expression of the target gene can be inhibited.
