The invention relates to a gas extraction device, and belongs to the technical field of gas extraction. The gas extraction device comprises an extraction pipe, wherein a purifying cylinder and a drying cylinder are arranged on the extraction pipe; one end, near the purifying cylinder, of the extraction pipe is connected with one end of a connecting pipe, and the other end of the connecting pipe isprovided with a circumference slide groove; one end of an electric telescopic rod is connected with the circumference slide groove, and the other end of the electric telescopic rod is connected witha fixed plate; air ventilating holes are formed in the surface of the fixed plate; a cleaning brush is arranged at one side, away from the connecting pipe, of the fixed plate; one end, with the circumference slide groove, of the connecting pipe is connected with an air suction cover; a filtering net is arranged at one side, away from the connecting pipe, of the air suction cover; a driver and an installation box are arranged at the outer wall of one end, connected with the connecting pipe, of the extraction pipe. The gas extraction device has the advantages that the structure is simple, and the installation is convenient; the automatic dedusting, gas drying and gas concentration detection functions are realized, the limitation by the conditions of working faces is avoided, the extraction position can be freely moved according to the detected gas concentration, and the concentration of gas at the working face does not exceed the limit.