[Object] To provide an arithmetic device, an arithmetic method, and a gas detection system that are capable of easily correcting deterioration over time of a detection element.
[Solving Means] The arithmetic device includes a calculation unit. The calculation unit calculates a correction coefficient from a detection element that causes a resonant frequency change by adsorption of gas on the basis of a resonant frequency change amount associated with a humidity change of the detection element in a degraded state and a resonant frequency change amount associated with a humidity change of the detection element in an initial state that was acquired in advance, and corrects the resonant frequency change amount of the detection element in the degraded state by using the correction coefficient.