A composition for the delivery of nucleic acid to target cells or tissues, which comprises polycationically charged polymer as a carrier of nucleic acid is provided. Said 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-(CH 2 ) a -(NH(CH 2 ) 2 ) e -NH 2 (wherein a and e independently denote an integer of 1 to 5) which is connected to said main chain either directly or via a linker. This composition is low-toxic, and has a high efficiency in introducing nucleic acid into cells.
