A gas sensor includes an element body, an inner main pump electrode, an inner auxiliary pump electrode, an inner preliminary pump electrode, a measurement electrode, a reference electrode, a measurement voltage detection device, a specific gas concentration detection device. The inner preliminary pump electrode, the inner main pump electrode, the inner auxiliary pump electrode and the measurement electrode include each contain a noble metal having catalytic activity. At least one of the inner preliminary pump electrode and the inner main pump electrode contains no noble metal having a catalytic activity suppression ability, the catalytic activity suppression ability being an ability to suppress the catalytic activity of the noble metal having the catalytic activity from being exhibited to the specific gas. The inner auxiliary pump electrode contains a noble metal having the catalytic activity suppression ability.