Abstract: A leukocyte separator for trapping and separating leukocytes from blood is made of a porous material having a bubble point ranging from 0.08 to 0.3 kg/cm.sup.2 and a thickness of at least 0.30 mm. The leukocyte separator is manufactured by pressing a porous material having a bubble point smaller than 0.13 kg/cm.sup.2 to produce a porous material having a thickness of at least 0.3 mm and a bubble point ranging from 0.13 to 0.3 kg/cm.sup.2.

Abstract: A liquid filtering device for separating leukocytes from blood to produce concentrated red cells, for example, includes a housing having a liquid inlet port and a liquid outlet port and providing a flow passage from the liquid inlet port to the liquid outlet port, a partition plate fixedly disposed in the housing, a first filter element disposed in the housing in an upstream position with respect to the flow passage, and a second filter element disposed in the housing in a downstream position with respect to the flow passage, the second filter element being made of a material having a larger filtration resistance than the first filter element. The second filter element has an outer peripheral edge fixed directly to the partition plate in a liquidtight manner in surrounding relation to the first filter element.