The invention relates to a simultaneous measurement device for gas chemical composition and noble gas isotope composition. The device comprises a noble gas mass spectrometer system, a quadrupole mass spectrometer, a high-vacuum system with a main pipeline, a cold trap and a titanium sponge furnace, wherein the main pipeline is respectively connected with a vacuum pipeline I, a vacuum pipeline II and a vacuum pipeline III; the tail end of the vacuum pipeline I is connected with the noble gas mass spectrometer system; the tail end of the vacuum pipeline II is respectively connected with a vacuum pipeline IV and a vacuum pipeline V; the tail end of the vacuum pipeline IV is connected with the quadrupole mass spectrometer; the tail end of the vacuum pipeline V is connected with the titanium sponge furnace; and the vacuum pipeline III is connected with a sampling port through the cold trap. The invention also discloses a simultaneous measurement method for gas chemical composition and noble gas isotope composition. The simultaneous measurement device provided by the invention feeds a sample at one time, is comprehensive in measurement result, not only corrects the mixed air interference in the gas sampling and transporting processes but also corrects the interference of air mixed in the process of transferring the sample to the instrument for analysis.