The present invention relates to a porous fiber that suppresses the exposure and separation of powder and granules while improving the adsorption performance, an adsorption column filled with the porous fiber, and a blood purification system in which the adsorption column and the water removal column are connected. The purpose is to provide. In order to achieve the above object, the porous fiber of the present invention has the following constitution. That is, it is a porous fiber having a three-dimensional pore structure formed by solid-shaped fibers and satisfying all the following requirements. (1) The powder having a diameter of 200 μm or less has an area occupancy of 3.0% or more in the cross section of the three-dimensional pore structure of the powder having a diameter of 200 μm or less. A region within 1.0 μm in the depth direction from the outermost surface does not include the above-mentioned powder having a diameter of 200 μm or less.本発明は、粉粒体の露出や剥離の抑制と、吸着性能の向上を両立した多孔質繊維、その多孔質繊維を充填した吸着カラム、及び吸着カラムと除水カラムを連結した血液浄化システムを提供することを目的とする。 上記目的を達するため、本発明の多孔質繊維は以下の構成を有する。すなわち、中実形状の繊維により形成された３次元細孔構造を有し、次の要件をすべて満たす多孔質繊維である。（１）直径２００μｍ以下の粉粒体を有するものであり、前記直径２００μｍ以下の粉粒体の、前記３次元細孔構造の横断面における面積占有率が３．０％以上である（２）最表面から深さ方向に１．０μｍ以内の領域には前記直径２００μｍ以下の粉粒体を含まないものである
