A permselective separation membrane which is a hollow fiber membrane and (a) the permselective separation membrane is made of a polysulfone-based polymer and polyvinyl pyrrolidone; and is characterized in that: (b) when bovine blood at a temperature of 37 °C having hematocrit value of 30%, containing 6 to 7 g/dl of total proteins and sodium citrate added thereto is flowed through a module comprising the permselective separation membrane packed therein at a flow rate of 200 ml/min. and a filtration rate of 20 ml/min., (i) a sieving coefficient of albumin becomes not less than 0.01 and not more than 0.1 after 15 minutes; and (ii) a sieving coefficient of albumin becomes not less than 0.005 and less than 0.04 after 2 hours; (c) the skin layer thickness of a skin layer provided on the inner surface of the permselective separation membrane, determined by observing a cross-section of the hollow fiber membrane with a scanning electron microscope with a magnification of 3000 times and measuring the thickness of a portion where holes cannot be observed and which is defined as the skin layer, is from 0.1 to 1.2 μm; (d) the membrane thickness of the permselective separation membrane is from 25 to 45 μm; and (e) the polyvinyl pyrrolidone content in the uppermost layer on the outer surface of the permselective separation membrane, determined by ESCA as defined herein, is from 25 to 50% by weight, and a ratio / between the polyvinyl pyrrolidone content in the uppermost layer of the outer surface and the polyvinyl pyrrolidone content in the uppermost layer of the inner surface, determined by ESCA as defined herein, is in the range of 1.1 to 1.9. (a) the permselective separation membrane is made of a polysulfone-based polymer and polyvinyl pyrrolidone; (b) when bovine blood at a temperature of 37 °C having hematocrit value of 30%, containing 6 to 7 g/dl of total proteins and sodium citrate added thereto is flowed through a module comprising the permselective separation membrane packed therein at a flow rate of 200 ml/min. and a filtration rate of 20 ml/min., (i) a sieving coefficient of albumin becomes not less than 0.01 and not more than 0.1 after 15 minutes; and (ii) a sieving coefficient of albumin becomes not less than 0.005 and less than 0.04 after 2 hours; (i) a sieving coefficient of albumin becomes not less than 0.01 and not more than 0.1 after 15 minutes; and (ii) a sieving coefficient of albumin becomes not less than 0.005 and less than 0.04 after 2 hours; (c) the skin layer thickness of a skin layer provided on the inner surface of the permselective separation membrane, determined by observing a cross-section of the hollow fiber membrane with a scanning electron microscope with a magnification of 3000 times and measuring the thickness of a portion where holes cannot be observed and which is defined as the skin layer, is from 0.1 to 1.2 μm; (d) the membrane thickness of the permselective separation membrane is from 25 to 45 μm; and (e) the polyvinyl pyrrolidone content in the uppermost layer on the outer surface of the permselective separation membrane, determined by ESCA as defined herein, is from 25 to 50% by weight, and a ratio / between the polyvinyl pyrrolidone content in the uppermost layer of the outer surface and the polyvinyl pyrrolidone content in the uppermost layer of the inner surface, determined by ESCA as defined herein, is in the range of 1.1 to 1.9.