A microdevice made of glass for genetic analysis has been fabricated, for the first time, for integration of extraction of nucleic acids and loop-mediated isothermal amplification (LAMP), followed by online fluorescence detection of amplification products on a single chip. The nucleic acid (NA) extraction region consists of a microfabricated serpentine channel in which micropillars were etched to increase the channel surface area and the capture efficiency of NAs. Nucleic acid molecules were bound to these pillars and channel surface in the presence of the chaotropic salt guanidine hydrochloride and eluted into a downstream amplification chamber with low ionic strength buffer where loop-mediated isothermal amplification was efficiently performed. Amplification can be detected online by the increase of fluorescence intensity at 540 nm when a low concentration of SYBR Green I, a fluorescent dsDNA intercalating dye, is employed. Flow control was accomplished by using laminar flow and differential channel flow resistances. Through passivation of the LAMP chamber and the channel between the extraction region and amplification domain, effective nucleic acid extraction and amplification were performed by just using a double-channel syringe pump and a heating block. By using this integrated microdevice, the purification of nucleic acids from complex biological matrixes and their subsequent amplification and detection online could be finished within 2 h.