Provided is a hydrogen ion sensor including: a substrate having a well and a first contact, the well having a second, a third, a fourth and a fifth contacts, the second contact having the same conductive type as the well, and the third, the fourth, and the fifth contacts having an opposite conductive type to the well; a first gate insulation layer on a region between the fourth contact and the fifth contact; a second gate insulation layer on a region between the third contact and the fourth contact; and a hydrogen ion sensing unit formed on the first gate insulation layer, wherein the hydrogen ion sensing unit transfers a voltage level adjusted according to a hydrogen ion concentration of a solution to be measured, to the first gate insulation layer.