A gas detection method using a gas detection element obtained by laminating a fixed support, a first electrode (2), a dielectric sensor (3), a second electrode (4), and a gas adsorption film (5), in this order, the method including: a step of applying a first signal resonantly driving the dielectric sensor (3) between electrodes of the first electrode (1) and the second electrode (3), and detecting gas adsorbed on the gas adsorption film based on a change of a resonant frequency of the dielectric sensor; and a step of heating the dielectric sensor (3) by applying a second signal between the electrodes after the detection of gas and desorbing gas adsorbed in the gas adsorption film; a gas detection system capable of performing the method; and a gas desorption method appropriate for applying this gas detection method.