The polysaccharide derivative of the present invention has a partial structure represented by the following general formula (1). It is preferable that at least one of the amino acids constituting X2 of the following general formula (1) is a basic amino acid. (Wherein X1 represents a residue obtained by removing a terminal amino group and a terminal carboxyl group from a neutral amino acid or ω-aminoalkanoic acid, and 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 the number of 0 or 1, and b represents the number of 0 to 50.)本発明の多糖誘導体は、下記一般式（１）で表される部分構造を有する。下記一般式（１）のＸ2を構成するアミノ酸の少なくとも１つが塩基性アミノ酸であることが好ましい。（式中、Ｘ1は、中性アミノ酸又はω－アミノアルカン酸から末端アミノ基及び末端カルボキシル基を除いた残基を表し、Ｘ2は膜透過性ペプチドから末端アミノ基及び末端カルボキシル基を除いた残基を表し、Ｘ3は、水酸基、アミノ基、炭素数１～４のアルコキシル基又はベンジルオキシ基を表し、ａは０又は１の数を表し、ｂは０～５０の数を表す。）
