If these characteristics of the LAMP method are used effectively, we believe it will be possible to develop simple genetic testing devices that have not been realized yet despite a strong awareness of their necessity, in a wide range of fields, including infectious disease testing, food inspection, and environmental testing. The key to developing such simple devices will be figuring out how to simply and clearly present the final amplification results. The objective of this research is to establish new techniques for sequence-specific visual detection of amplification results by means of the LAMP method. To that end, we made use of a reaction that has been known for a long time, i.e., cationic polymers like polyamines form an insoluble complex with DNA [10] . It is well known that one of such the polyamine, polyethylenimine (PEI), strongly interacts with DNA. PEI is widely used as a nucleic acid precipitant for nucleic acid purification [11] and as an in vivo and in vitro non-viral vector [12, 13] . We discovered that an insoluble PEI-LAMP product complex was generated under certain optimized conditions when PEI was added to LAMP reaction solution. Using this precipitation titration, we investigated whether it was possible to perform bound/ free separation of fluorescently labeled probes. In this paper, we report the novel visual detection methods of the presence of sequences of HBV and HCV cloned to plasmid as a model experiment using this method and the results of an investigation of the basic reaction conditions required to achieve this.