To provide: a polysulfone-based membrane for treating blood which is excellent in antioxidant properties and storage stability over a long time, has a high practical strength and can be highly conveniently produced； a polysulfone-based membrane for treating blood which is excellent in antioxidant properties and storage stability over a long time, suffers from little risk of contamination of the liquid to be treated with an endotoxin, has a high practical strength and can be highly conveniently produced； ； and a method of producing the same. A polysulfone-based membrane for treating blood which comprises a polysulfone-based resin, a hydrophilic polymer and a fat-soluble antioxidant agent, characterized in that the membrane contains from 30 to 76 mg of the fat-soluble antioxidant agent per gram of the membrane and the total amount of the fat-soluble antioxidant agent present on the membrane surface is from 4 to 25 mg per gram of the membrane； a polysulfone-based membrane for treating blood which is further characterized in that the membrane contains from 30 to 76 mg of the fat-soluble antioxidant agent per gram of the membrane and the TOF-SIMS standard peak strength of the fat-soluble antioxidant agent is 1.8x10-4 or more on the inner surface of the membrane and 2.4x10-4 or more on the outer surface of the membrane； and a method of producing a membrane for treating blood which comprises a polysulfone-based resin, a hydrophilic polymer and a fat-soluble antioxidant agent, characterized by comprising preparing an intermediate membrane containing from 30 to 76 mg of a fat-soluble antioxidant agent per gram of the membrane and then heating the intermediate membrane in a dry state at 100 to 180oC for 0.1 to 360 minutes.本發明提供一種抗氧化性及長期保存穩定性優異，且具有實用強度，並且生產合理性較高之聚碸系血液處理膜；進而提供一種抗氧化性以及長期保存穩定性優異，同時內毒素侵入至處理液之危險性較小，且具有實用強度，並且生產合理性較高之聚碸系血液處理膜、及該處理膜之製造方法。；本發明係關於一種聚碸系血液處理膜，其特徵在於：其係包含聚碸系樹脂、親水性高分子及脂溶性抗氧化劑者，每1 g之該膜含有30~76 mg之脂溶性抗氧化劑，且每1 g之膜之存在於膜表面之脂溶性抗氧化劑的總和為4~25 mg；進而係關於一種聚碸系血液處理膜，其特徵在於
