The purpose of the present invention is to provide a technique for the simple and efficient acquisition of a nucleic acid extract which is ready for use in nucleic acid amplification reactions, even if a sample contains many contaminants. Cholic acid, glycolic acid, and a divalent cation chelator are brought into contact with a sample and a nucleic acid is extracted, after which albumin is added. Thus, even if the sample contains many contaminants, a nucleic acid extract ready for use in nucleic acid amplification reactions can be simply and efficiently acquired.