A gas sensor including: a gas sensing element (200) including first and second ceramic layers (241, 221). The first ceramic layer has a first through hole (241h1) and a first through hole conductor (271) covering an inner surface thereof. The first ceramic layer includes a first conductor (247) which includes: a first peripheral conductive portion (247c) electrically connected to the first through hole conductor (271); a first lead portion (247b) that is narrower than the first peripheral conductive portion (247c); and a first contact conductive portion (247a) that is wider than the first lead portion (247b). The first peripheral conductive portion (247c), the first lead portion (247b) and the first contact conductive portion (247a) are integrally formed and arranged in this order in a longitudinal direction. The second ceramic layer (221) includes a second conductor (222) electrically connected to at least the first contact conductive portion (247a).