Polyester fabrics, the surfaces of which were hydrolyzed with caustic soda solution to incorporate the functional groups (-COOH) were treated with chitosan to obtain the new available functions expected. The chitosan was fixed to the surface by the reaction of these carboxyl-groups and the amino-groups of the chitosan molecules. At the same time, the chitosan films on the fibers were insolublized by the cross-linking with dicarboxylic acids. The strength of the polyester fabrics was decreased greatly by the alkali-treatment but recovered by the chitosan-treatments. One of the functions obtained with the chitosan treatment was the remarkable antistaticity.