A new instrument for evolved gas analysis (EGA) has been developed using a skimmer interface and IA-QMS (Ion Attachment Quadrupole Mass Spectrometer). The skimmer interface is a new interface device between an infrared image furnace and an MS, for sampling of gaseous species produced by pyrolysis. It offers gas sampling with no change and higher sensitivity. The IA-QMS can measure a mass spectrum with no fragmentation during the ionization. As its application to pyrolysis of organic additives for ceramic processing, monitoring of individual polymer pyrolysis has been successfully carried out to pyrolytic gas evolution from mixtures of different polymers.