PURPOSE: To enable detection with high sensitivity, by forming an org. polymer comprising a heterocyclic 5-membered compound containing one oxygen or nitrogen group element.

CONSTITUTION: A support plate 1 comprises an insulating material such as glass or ceramic and is formed in such a comb shape that a pair of electrodes 2A, 2B are mutually engaged with the support plate 1 and a gas response film (org. polymer) 3 is formed so as to be interposed between the electrodes 2A, 2B. As the org. polymer, polypyrol or polythiophene is designated and a film or powdery shape org. polymer is synthesized by a chemical polymerization method or an electrolytic polymerization method. When decomposed gas is generated in the gas response film 3 comprising the org. polymer, said decomposed gas is diffused throughout the gas response film 3 and the change in conductivity is generated. Therefore, by detecting the change in the resistance value between electrodes 2A, 2B, the variation in a gaseous atmosphere can be detected.