Polymer compound which has membrane-permeable peptide in side chain

A polymer compound having a group represented by Formula (1) below or Formula (2) below in a side chain:

• wherein X1 represents a residue obtained by removing a terminal amino group and a terminal carboxyl group from glycine, X2 represents a residue obtained by removing a terminal amino group and a terminal carboxyl group from octaarginine, X3 represents a hydroxyl group, an amino group, an alkoxyl group having 1 to 4 carbon atoms, or a benzyloxy group, and “a” is 4;
• and
• wherein X4 represents a residue obtained by removing a terminal amino group and a terminal carboxyl group from glycine, X5 represents a residue obtained by removing a terminal amino group and a terminal carboxyl group from octaarginine, X6 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a benzyl group, an acyl group having 1 to 6 carbon atoms, an arylsulfonyl group, or an oxycarbonyl group, and “b” is 4;
• said polymer compound comprising acrylic acid-N-vinylacetamide copolymer as a stem polymer.