A sulfur oxides detection system comprising: a device part arranged in an exhaust passage of an internal combustion engine and comprising a first electrochemical cell having a first solid electrolyte layer having oxide ion conductivity, a first electrode arranged on one surface of the first solid electrolyte layer so as to be exposed to measured gas, and a second electrode arranged on the other surface of the first solid electrolyte layer so as to be exposed to the atmospheric air, and a diffusion regulating layer regulating diffusion of the measured gas; a power supply (61, 71) supplying voltage across the first electrode and the second electrode; a detector (62, 72) detecting a first current correlation parameter correlated with a current flowing between the first electrode and the second electrode; and a control part controlling the power supply (61, 71) and acquiring the first current correlation parameter from the detector (62, 72), characterized in that the control part is arranged to control the power supply (61, 71) so that a first voltage which is a decomposition start voltage of water and sulfur oxides or more is applied across the first electrode and the second electrode and to calculate a concentration of sulfur oxides in the measured gas based on the first current correlation parameter detected by the detector (62, 72) when the first voltage is applied across the first electrode and the second electrode and the control part is further arranged not to calculate the concentration of sulfur oxides in the measured gas when the control part judges that a concentration of water in the measured gas is not stable. a device part arranged in an exhaust passage of an internal combustion engine and comprising a first electrochemical cell having a first solid electrolyte layer having oxide ion conductivity, a first electrode arranged on one surface of the first solid electrolyte layer so as to be exposed to measured gas, and a second electrode arranged on the other surface of the first solid electrolyte layer so as to be exposed to the atmospheric air, and a diffusion regulating layer regulating diffusion of the measured gas; a power supply (61, 71) supplying voltage across the first electrode and the second electrode; a detector (62, 72) detecting a first current correlation parameter correlated with a current flowing between the first electrode and the second electrode; and a control part controlling the power supply (61, 71) and acquiring the first current correlation parameter from the detector (62, 72), characterized in that the control part is arranged to control the power supply (61, 71) so that a first voltage which is a decomposition start voltage of water and sulfur oxides or more is applied across the first electrode and the second electrode and to calculate a concentration of sulfur oxides in the measured gas based on the first current correlation parameter detected by the detector (62, 72) when the first voltage is applied across the first electrode and the second electrode and the control part is further arranged not to calculate the concentration of sulfur oxides in the measured gas when the control part judges that a concentration of water in the measured gas is not stable.