Patent ID: 8881914

Claim:
A blood processing filter comprising a sheet-like filter element, an inlet-side flexible container and an outlet-side flexible container that sandwich the filter element and are sealed thereto, an inlet port provided in the inlet-side flexible container for accepting blood before being processed by the filter element, and an outlet port provided in the outlet-side flexible container for discharging blood after being processed by the filter element; the blood processing filter further comprising: a flow channel securing sheet that is arranged between the filter element and the outlet-side flexible container; a frame sheet that is arranged between the filter element and the inlet-side flexible container; a first seal part that, in a state in which the filter element is clamped by the frame sheet and the flow channel securing sheet, seals the frame sheet, the filter element, and the flow channel securing sheet in a band shape, and that is provided in a ring shape along a periphery of the filter element; an opening formed in the frame sheet at an inner side that is surrounded by the first seal part; a plurality of flow channel holes that are formed in the flow channel securing sheet and through which blood that is processed by the filter element passes, wherein: the outlet port is provided so as to be capable of communicating with the flow channel holes; an annular second seal part that seals at least the inlet-side flexible container, the frame sheet, the flow channel securing sheet, and the outlet-side flexible container, and the annular second seal part being provided so as to surround the first seal part at a position that is closer to an outer edge of the blood processing filter than is the first seal part; and a valley part corresponding to the first seal part that is provided on an outlet side of the filter element, wherein each of the flow channel holes have a slit shape, and wherein opposing ends of at least one of the flow channel holes are arranged in the empty space region that is formed by the valley part, in the state in which blood is flowing.