An SO x gas sensor comprising: a gas reduction chamber in which SO x gas included in sample gas is reduced; a gas measurement chamber in which the concentration of the reduced SO x gas generated in the gas reduction chamber is measured while the reduced SO x gas is being oxidized; a first solid electrolyte composing a part of a wall of the gas reduction chamber and provided with a first gas introducing hole for introducing the sample gas into the gas reduction chamber, an oxidation part made of a material including an oxidation catalyst and provided in the first gas introducing hole for oxidizing noise gas other than the SO x gas included in the sample gas, and a reduction mechanism including a first electrode and a second electrode provided on the first solid electrolyte configured for reducing in the gas reduction chamber the SO x gas included in the sample gas after oxidation by the oxidation part; a communication unit provided between the gas reduction chamber and the gas measurement chamber to partition the gas reduction chamber and the gas measurement chamber and provided with a second gas introducing hole for introducing the reduced SOx gas into the gas measurement chamber from the gas reduction chamber, and a gas diffusion resistor provided in the second gas introducing hole; and a second solid electrolyte composing a part of a wall of the gas measurement chamber and provided with an oxidation mechanism including a third electrode and a fourth electrode provided on the second solid electrolyte configured for oxidizing in the gas measurement chamber the reduced SO x gas generated in the gas reduction chamber, and a measurement mechanism including a measurement electrode provided on the second solid electrolyte configured for measuring the concentration of the reduced SO x gas introduced into the gas measurement chamber from the gas reduction chamber and being oxidized in the in the gas measurement chamber. a gas reduction chamber in which SO x gas included in sample gas is reduced; a gas measurement chamber in which the concentration of the reduced SO x gas generated in the gas reduction chamber is measured while the reduced SO x gas is being oxidized; a first solid electrolyte composing a part of a wall of the gas reduction chamber and provided with a first gas introducing hole for introducing the sample gas into the gas reduction chamber, an oxidation part made of a material including an oxidation catalyst and provided in the first gas introducing hole for oxidizing noise gas other than the SO x gas included in the sample gas, and a reduction mechanism including a first electrode and a second electrode provided on the first solid electrolyte configured for reducing in the gas reduction chamber the SO x gas included in the sample gas after oxidation by the oxidation part; a first gas introducing hole for introducing the sample gas into the gas reduction chamber, an oxidation part made of a material including an oxidation catalyst and provided in the first gas introducing hole for oxidizing noise gas other than the SO x gas included in the sample gas, and a reduction mechanism including a first electrode and a second electrode provided on the first solid electrolyte configured for reducing in the gas reduction chamber the SO x gas included in the sample gas after oxidation by the oxidation part; a communication unit provided between the gas reduction chamber and the gas measurement chamber to partition the gas reduction chamber and the gas measurement chamber and provided with a second gas introducing hole for introducing the reduced SOx gas into the gas measurement chamber from the gas reduction chamber, and a gas diffusion resistor provided in the second gas introducing hole; and a second gas introducing hole for introducing the reduced SOx gas into the gas measurement chamber from the gas reduction chamber, and a gas diffusion resistor provided in the second gas introducing hole; and a second solid electrolyte composing a part of a wall of the gas measurement chamber and provided with an oxidation mechanism including a third electrode and a fourth electrode provided on the second solid electrolyte configured for oxidizing in the gas measurement chamber the reduced SO x gas generated in the gas reduction chamber, and a measurement mechanism including a measurement electrode provided on the second solid electrolyte configured for measuring the concentration of the reduced SO x gas introduced into the gas measurement chamber from the gas reduction chamber and being oxidized in the in the gas measurement chamber. an oxidation mechanism including a third electrode and a fourth electrode provided on the second solid electrolyte configured for oxidizing in the gas measurement chamber the reduced SO x gas generated in the gas reduction chamber, and a measurement mechanism including a measurement electrode provided on the second solid electrolyte configured for measuring the concentration of the reduced SO x gas introduced into the gas measurement chamber from the gas reduction chamber and being oxidized in the in the gas measurement chamber.