The present invention aims to provide a novel nucleic acid molecule that can be produced easily and efficiently, and can inhibit gene expression.Provided is a single-stranded nucleic acid molecule containing an expression inhibitory sequence that inhibits expression of a target gene, and containing region (X), linker region (Lx) and region (Xc), wherein the linker region (Lx) is linked between the region (Xc) and the region (Xc), the region (Xc) is complementary to the region (X), at least one of the region (X) and the region (Xc) contains the expression inhibitory sequence, and the linker region (Lx) contains an atomic group derived from an amino acid. The single-stranded nucleic acid molecule can inhibit expression of the above target gene.
