A polysaccharide derivative has a partial structure represented by Formula (1) below. It is preferable that at least one of the amino acids that constitute X2 in Formula (1) below is a basic amino acid. (In the formula, X1 represents a residue obtained by removing the terminal amino group and the terminal carboxyl group from a neutral amino acid or an ω-aminoalkanoic acid, X2 represents a residue obtained by removing the terminal amino group and the terminal carboxyl group from a membrane-permeable peptide, X3 represents a hydroxyl group, an amino group, an alkoxyl group having 1 to 4 carbon atoms, or a benzyloxy group, a represents a number of 0 or 1, and b represents a number of from 0 to 50.)