A gas sensor is provided with a metal shell protecting member formed of a material superior in heat resistance to a metal shell, whereby a high-temperature measurement target (exhaust gas) is prevented from being in direct contact with a region, of a protector internal region of the metal shell, on the front side relative to a protector opposing surface. That is, in the gas sensor, it is possible to suppress corrosion, due to high temperature, of a region, of the protector internal region of the metal shell, on the front side relative to the protector opposing surface (an inner surface and a front end surface of a protector fixing portion), while the metal shell is formed of a material (SUS430) that can be subjected to working (crimping or the like) accompanied with deformation. Therefore, heat resistance of the entire sensor can be improved.