Device for the photoacoustic detection of at least one gas, characterised in that it comprises: - a Helmholtz-type resonant tank consisting of two primary tubes (105, 106), whose ends are closed, connected to each other near their extremities by two secondary tubes (109, 110); - a means for introducing gas (118, 119) in said tank; - at least one first source of radiant laser energy modulated to a first resonance frequency of the tank, which supplies an excitation energy in at least one of the primary tubes, with an emission wavelength matching a local maximum absorption wavelength for a first gas, each said first source of radiant energy being positioned opposite a window closing a primary tube extremity, to generate a first standing wave propagating along the secondary tubes; - at least one second source of radiant energy modulated to a second resonance frequency of the tank, which supplies an excitation energy in at least one of the secondary tubes, with an emission wavelength matching a local maximum absorption wavelength for a second gas, each said first source of radiant energy being positioned opposite a window closing a primary tube extremity, to generate a second standing wave propagating along the primary tubes; - at least one acoustoelectric transducer (103, 104, 123, 124) arranged on a wall of each tube for detecting the acoustic signals produced in said tube; - a means for processing the signals coming from the transducers positioned on the primary tubes, to extract an amplitude of the first standing wave; and - a means for processing the signals coming from the transducers positioned on the secondary tubes, to extract an amplitude of the second standing wave. - a Helmholtz-type resonant tank consisting of two primary tubes (105, 106), whose ends are closed, connected to each other near their extremities by two secondary tubes (109, 110); - a means for introducing gas (118, 119) in said tank; - at least one first source of radiant laser energy modulated to a first resonance frequency of the tank, which supplies an excitation energy in at least one of the primary tubes, with an emission wavelength matching a local maximum absorption wavelength for a first gas, each said first source of radiant energy being positioned opposite a window closing a primary tube extremity, to generate a first standing wave propagating along the secondary tubes; - at least one second source of radiant energy modulated to a second resonance frequency of the tank, which supplies an excitation energy in at least one of the secondary tubes, with an emission wavelength matching a local maximum absorption wavelength for a second gas, each said first source of radiant energy being positioned opposite a window closing a primary tube extremity, to generate a second standing wave propagating along the primary tubes; - at least one acoustoelectric transducer (103, 104, 123, 124) arranged on a wall of each tube for detecting the acoustic signals produced in said tube; - a means for processing the signals coming from the transducers positioned on the primary tubes, to extract an amplitude of the first standing wave; and - a means for processing the signals coming from the transducers positioned on the secondary tubes, to extract an amplitude of the second standing wave.