A nucleic acid adsorbent in which a polymer having a constitutional unit represented by the following formula (I) 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.sub.1 represents hydrogen, fluoride, or methyl; R.sub.2 and R.sub.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.