The present invention relates to a polysaccharide derivative which can improve the cleanability of laundry and the like, and can suppress recontamination caused by powdery dirt during washing. The present invention is a polysaccharide derivative having a cationic group and a hydrocarbon group (R) having 2 or more carbon atoms, and the above hydrocarbon group (R) is directly or via a hydrocarbon group having an oxygen atom and a self-hydroxyalkane a base bond formed by removing a hydrogen atom from a hydroxyl group of a polysaccharide, the hydroxyalkylated polysaccharide being a hydroxyethylated polysaccharide or a hydroxypropylated polysaccharide, and the weight average molecular weight of the above hydroxyalkylated polysaccharide is 10,000 or more and 74 Less than 10,000.本發明係關於一種可提高衣物等之清洗性，並且可抑制清洗時之粉體污垢導致之再污染的多糖衍生物。本發明係一種多糖衍生物，其係具有陽離子性基、及碳數為2以上之烴基(R)者，且上述烴基(R)係直接、或藉由具有氧原子之烴基而與自羥基烷基化多糖之羥基中去掉氫原子而成之基鍵結，羥基烷基化多糖為羥基乙基化多糖或羥基丙基化多糖，上述羥基烷基化多糖之重量平均分子量為1萬以上且74萬以下。
