The invention relates to a stimulus-responding polymer obtained by polymerizing at least a monomer represented by a general formula (1) and a monomer represented by a general formula (2), and a separation method or concentration method of microorganisms, a purification method, detection method or concentration method of nucleic acids, a separating agent, a separation method of biomaterials and a conversion method of materials, which use this polymer,
(in the formula, R11 represents hydrogen atom or methyl group, and R12 represents single bond or a straight or branched alkylene group having from 1 to 5 carbon atoms)
(in the formula, R13 represents hydrogen atom or methyl group, and R14 represents hydrogen atom, a straight, branched or cyclic alkyl group, alkoxyl group or alkylamino group having from 1 to 10 carbon atoms, an aryl group or a heterocyclic group).