The present invention is affinity particles that are characterized by having phosphorylcholine groups represented by the following formula (1) covalently bonded onto the surface of inorganic powder and also by having ligands having specific affinity with a certain target substance covalently bonded or adsorbed onto the surface of inorganic powder. The object of the present invention is to provide an affinity separation method that uses affinity particles utilizing inexpensive inorganic particles and is capable of separating the target substance easily and with high accuracy. ##STR00001##