Filter for removal of leucocytes is provided, wherein the filter is coated with a natural polymer of chitosan which has a good blood compatibility and no side effect in human body on an ultrafine non-woven fabric. This blood filter provides a high removal rate of leucocytes as well as good recovery of platelets and red blood cells due to secondary filtration through electrostatic power between a leucocyte and a cationic residue provided by chitosan on the surface of the non-woven fabric.