A thermosensitive microgel adsorbent, which adsorbs and desorbs a specific heavy metal ion by the temperature swing, was developed. The microgels was prepared by the emulsion polymerization using anionic polymerizable surfactant. N-Isopropylacrylamide (NIPA) and N-(4-vinyl)benzyl ethylenediamine were used as the primary monomer and the chelating monomer, respectively. In the preparation, the molecular imprinting technique using Cu(II) ions as a target heavy metal ion was adopted. The thermosensitive microgel adsorbents were dispersed stably even if the temperature of the suspension exceeded the transition temperature of poly(NIPA), and Cu(II) ions were adsorbed quickly in response to the temperature change.