Described is a method for producing highly pure LPF-HA (Leucocytosis-promoting Factor Hemagglutinin) from culture media of Bordetella pertussis in a high yield by an affinity chromatography using a denatured ceruloplasmin as a ligand. The LPF-HA obtained by this invention is highly pure and contains almost no endotoxin of B. pertussis and is useful for the preparation of various reagents utilizing the physiological activities, of a medicine for treating diabetes and of a pertussis vaccine.