A graphite-based sensor includes an undoped graphite structure that adsorbs foreign atoms and molecules. A magnetization detection device includes a substrate on which the graphite structure is adhered, a current source by which a current is applied to the substrate and the graphite structure, and a voltage measuring device coupled to the substrate. When the graphite structure adsorbs the gas molecules, the graphite structure exhibits a ferromagnetic-type behavior, and a corresponding voltage generated in the magnetic detection device changes.