Protein adsorbent

A method for producing a protein adsorbent comprising a substrate and a molecular chain fixed to a surface of the substrate, the method comprising, in this order:

• a dry-heat treatment step of heating a pretreatment adsorbent comprising the substrate and the molecular chain fixed on the surface of the substrate, the molecular chain comprising a weak electrolytic ion-exchange group;
• and
• a wet-heat treatment step of heating the dry-heated adsorbent in a moistened state with a liquid selected from pure water, a buffer solution, an inorganic salt aqueous solution, and a buffer solution comprising an inorganic salt, or steam thereof, and
• wherein the moistened state of the protein adsorbent is maintained after the wet-heat treatment step to obtain the protein adsorbent.