An object of the invention is to provide a gas detection system that does not require customization of an odor sensor depending on an environment. The gas detection system includes a sensor array including a plurality of sensors having different characteristic sensitivities, a pre-processing unit configured to convert each of sensor output values acquired from the sensors constituting the sensor array into an output ratio as a ratio of the output value to a predetermined value, and an odor determination processing unit configured to determine, by comparing a normal range generated based on a result of executing cluster analysis on an output ratio acquired from each of the sensors constituting the sensor array in the past with the output ratio obtained by the pre-processing unit executing the conversion, whether the output ratio is within the normal range.