Provided are a method of conveniently and efficiently removing abnormal prion protein from a blood product and a method of removing leukocyte simultaneously with abnormal prion protein. The method of removing an abnormal prion protein from a blood product includes filtering the blood product through a filter filled with a carrier coated with a polymer, which is composed of three units including 20 mol % or more and 40 mol % or less of a unit originating from a hydrophobic polymerizable monomer, 5 mol % or more and 13 mol % or less of a unit originating from a polymerizable monomer containing a basic nitrogen-containing part, and a unit originating from a polymerizable monomer containing a protonic neutral hydrophilic part as the balance, and then recovering the filtered blood product.