A method of detecting a nucleic acid including a) mixing a solution containing a carboxylic acid and/or a salt thereof, a cerium oxide support and a sample containing a nucleic acid to adsorb said nucleic acid to said cerium oxide support, b) separating said cerium oxide support on which said nucleic acid was adsorbed from the mixture obtained in a), c) collecting said nucleic acid by adding an eluent to said cerium oxide support on which said nucleic acid was adsorbed and separated in b), and d) detecting said nucleic acid collected in c) by a hybridization reaction or a nucleic acid amplification reaction.