The object of the present invention is to provide a method capable of analyzing the presence or absence of a target DNA sequence, the level and sequence characteristics thereof at a high sensitivity, and a device therefor, wherein the overall process from pretreatment to the recovery of DNA information and the analysis thereof can be completed in a speedy fashion by the simple device structure and procedures. Therefore, by preparing a single-stranded DNA fragment of a target DNA region, detecting the change in the absorbance of the single-stranded DNA sample while changing the denaturing condition of the conformation of the single-stranded DNA fragment by a denaturing condition regulatory means, and analyzing the curve of the change in the absorbance over the modification in the denaturing condition, the sequence information of the single-stranded DNA, namely the target DNA, can be generated in a rapid and simple manner.