Disclosed is a composition for the delivery of nucleic acid to target cells or tissues, which comprises a polycationically charged polymer as a carrier of nucleic acid. The polycationically charged polymer is a polymer which may comprise a charged polymer segment having a main chain based on poly(amino acid), polysaccharide, polyester, polyether, polyurethane or vinyl polymer and having, as a side chain, a group of formula —NH—(CH2)a—(NH(CH2)2)e—NH2 (wherein a and e independently denote an integer of 1 to 5) which is connected to the main chain either directly or via a linker. The disclosed composition has low toxicity, and has a high efficiency in introducing nucleic acid into cells.