a nucleic acid adsorbent in which a polymer having a constitutional unit represented by the following formula is immobilized on a water - insoluble carrier is used as a nucleic acid adsorbent capable of selectively and efficiently adsorbing nucleic acids from complex mixtures , such as cell extract , wherein r 1 represents hydrogen , fluoride , or methyl ; r 2 and r 3 each independently represent alkyl of 1 to 6 carbon atoms ; a is — nh — or — o —; and b represents alkylene of 2 to 18 carbon atoms . nucleic acids are recovered from cell extract by allowing them to be adsorbed to the nucleic acid adsorbent by mixing this nucleic acid adsorbent with cell extract , removing the nucleic acids from the cell extract by separating the adsorbent therefrom , and dissociating the nucleic acids from the nucleic acid adsorbent by treating the separated nucleic acid adsorbent with alkali .