By reducing the clogging of the leukocyte removal filter material by plasma proteins and blood cell component, which is a problem when removing leukocytes in the blood, a high leukocyte removal performance in ambient temperature and filtered, to reduce the filtration time in cold storage during filtration that it provides a method for removing leukocytes exert. A leukocyte removal method of filtering the blood containing leukocytes using a leukocyte removal filter apparatus comprising a fibrous filter media having different average fiber diameters to remove the leukocytes from the blood, at least, fibrous filter medium of the plurality of average and a leukocyte removal filter medium for B is more than 0.7μm 1.2μm below and leukocyte removal filter medium for A fibers have a diameter of less than 4.0μm 2.0μm or more, filtrate material B is disposed on the downstream side of the filtrate material A , and leukocyte removal method is characterized in that the average fiber diameter of the leukocyte removal filter medium for B is using a leukocyte removal filter device, which is less than 50% greater than 17.5% of the filter medium A.血液中の白血球を除去する際に問題となる血球成分や血漿タンパクによる白血球除去用濾材の目詰まりを低減することで、冷蔵濾過時の濾過時間を短縮し、かつ室温濾過において高い白血球除去性能を発揮する白血球除去方法を提供すること。平均繊維直径の異なる複数の繊維状濾材を有する白血球除去フィルター装置を用いて白血球を含む血液を濾過し、血液から白血球を除去する白血球除去方法であって、該複数の繊維状濾材は少なくとも、平均繊維直径が2.0μm以上4.0μm未満である白血球除去用濾材A及び0.7μm以上1.2μm以下である白血球除去用濾材Bを含み、該濾材Bが該濾材Aの下流側に配置され、かつ白血球除去用濾材Bの平均繊維直径が濾材Aの17.5%より大きく50%未満である白血球除去フィルター装置を用いることを特徴とする白血球除去方法。
