A gas sensor comprising: a plate-shaped gas sensing element extending in a longitudinal direction and comprising a sensing portion provided at a leading-end side in the longitudinal direction, the gas sensing element comprising a plurality of stacked ceramic layers (211, 221, 231, 241) including a first ceramic layer having a first surface and a second ceramic layer having a second surface opposing the first surface, wherein the first ceramic layer has a first through hole (241h1), a first through hole conductor covering at least an inner surface of the first through hole (241h1), wherein the first ceramic layer comprises a first conductor formed on the first surface thereof, and wherein the second ceramic layer comprises a second conductor formed on the second surface thereof, wherein the first conductor comprises: a first peripheral conductive portion provided at a periphery of the first through hole (241h1) and electrically connected to the first through hole conductor; a first lead portion; and a first contact conductive portion, wherein the second conductor is electrically connected to at least the first contact conductive portion, wherein the first peripheral conductive portion, the first lead portion and the first contact conductive portion are integrally formed and arranged in this order in the longitudinal direction, wherein the first lead portion is narrower by at least 10% in a width direction perpendicular to the longitudinal direction than the first peripheral conductive portion, and the first contact conductive portion, wherein the second ceramic layer has a second through hole (221h1) with a second through hole conductor covering at least an inner surface of the second through hole (221h1), the second through hole (221h1) being connected to the first through hole (241h1), wherein the second conductor comprises: a second peripheral conductive portion provided at a periphery of the second through hole (221h1) and electrically connected to the second through hole conductor; a second lead portion; and a second contact conductive portion, wherein the second lead portion is narrower by at least 10% than the second peripheral conductive portion and the second contact conductive portion, wherein the second peripheral conductive portion, the second lead portion and the second contact conductive portion are integrally formed and arranged in this order in the longitudinal direction, and wherein at least the first contact conductive portion and the second contact conductive portion are electrically connected to each other. a plate-shaped gas sensing element extending in a longitudinal direction and comprising a sensing portion provided at a leading-end side in the longitudinal direction, the gas sensing element comprising a plurality of stacked ceramic layers (211, 221, 231, 241) including a first ceramic layer having a first surface and a second ceramic layer having a second surface opposing the first surface, wherein the first ceramic layer has a first through hole (241h1), a first through hole conductor covering at least an inner surface of the first through hole (241h1), wherein the first ceramic layer comprises a first conductor formed on the first surface thereof, and wherein the second ceramic layer comprises a second conductor formed on the second surface thereof, wherein the first conductor comprises: a first peripheral conductive portion provided at a periphery of the first through hole (241h1) and electrically connected to the first through hole conductor; a first lead portion; and a first contact conductive portion, a first peripheral conductive portion provided at a periphery of the first through hole (241h1) and electrically connected to the first through hole conductor; a first lead portion; and a first contact conductive portion, wherein the second conductor is electrically connected to at least the first contact conductive portion, wherein the first peripheral conductive portion, the first lead portion and the first contact conductive portion are integrally formed and arranged in this order in the longitudinal direction, wherein the first lead portion is narrower by at least 10% in a width direction perpendicular to the longitudinal direction than the first peripheral conductive portion, and the first contact conductive portion, wherein the second ceramic layer has a second through hole (221h1) with a second through hole conductor covering at least an inner surface of the second through hole (221h1), the second through hole (221h1) being connected to the first through hole (241h1), wherein the second conductor comprises: a second peripheral conductive portion provided at a periphery of the second through hole (221h1) and electrically connected to the second through hole conductor; a second lead portion; and a second contact conductive portion, wherein the second lead portion is narrower by at least 10% than the second peripheral conductive portion and the second contact conductive portion, wherein the second peripheral conductive portion, the second lead portion and the second contact conductive portion are integrally formed and arranged in this order in the longitudinal direction, and wherein at least the first contact conductive portion and the second contact conductive portion are electrically connected to each other.