Provided is a single-stranded nucleic acid capable of inhibiting expression of a target gene having a delivery function.A molecule containing, from the 5-side to the 3-side, a 5-side region (Xc), a linker region (Lx), an inner region (Z), a linker region (Ly) and a 3-side region (Yc) in this order, whereinthe aforementioned inner region (Z) is constituted by linkage of the inner 5-side region (X) and the inner 3-side region (Y),the aforementioned 5-side region (Xc) is complementary to the aforementioned inner 5-side region (X),the aforementioned 3-side region (Yc) is complementary to the aforementioned inner 3-side region (Y),at least one of the aforementioned inner region (Z), the aforementioned 5-side region (Xc) and the aforementioned 3-side region (Yc) comprises an expression inhibitory sequence that inhibits expression of a target gene, andat least one selected from the group consisting of the 5-terminus, the 3-terminus, the aforementioned linker region (Lx) and the aforementioned linker region (Ly) is bound to a bio-related substance.
