A substrate includes: a base material; and chelators which are three dimensionally covalently bound to the base material at a density of 7.8.times.10.sup.15/mm.sup.3 or greater and 4.5.times.10.sup.17/mm.sup.3 or less, or two dimensionally covalently bound to the base material at a planar density of 2.0.times.10.sup.11/mm.sup.2 or greater and 1.0.times.10.sup.13/mm.sup.2 or less. Metal ions are coordinately bound to the chelators, and a bioactive substance having histidine tags are coordinately bound to the metal ions. A blocking agent having ligand sets are coordinately bound to the metal ions to which the bioactive substance is not coordinately bound.