A semiconductor DNA sensing device having a detection section is provided. The detection section comprises a structure of a probe DNA/a first organic monolayer/an insulating layer/a semiconductor. The field-effect transistor (FET) comprises a semiconductor substrate and a first insulator layer formed thereon as a reactive gate insulator, and the first insulating layer comprises silicon oxide or an inorganic oxide. The first organic monolayer formed on the first insulator layer comprises an organic molecule having a reactive functional group. The probe DNA contains 3 to 35 nucleotides, and this probe DNA is bonded to the first organic monolayer by the reactive functional group either directly or by an intervening crosslinker. The semiconductor DNA sensing device of the present invention is extremely effective as an on-chip, high-sensitivity, micro multi-DNA sensing device, and an integrated device produced by using such semiconductor DNA sensing device is capable of sensing a DNA including a mismatch sequence such as single nucleotide polymorphism, and such device is indispensable for an advanced medicine and personalized medicine.