In the present invention, an amplified DNA fragment having a first substance binding site to which a first substance is specifically bindable is prepared, which amplified DNA fragment amplified by a nucleic acid amplification method. The amplified DNA fragment is concentrated by binding the amplified DNA fragment to the first substance. The concentration makes it possible to detect the DNA highly sensitively. Therefore, with the arrangement, it is possible to detect the amplified DNA fragment amplified by the nucleic acid amplification method, easily and highly accurately without requiring any special device.