PURPOSE: To detect an organic molecule with high sensitivity by detecting the change of an electric signal due to an externally functional organic molecule of an ion-conductive high molecular composition wherein the intersecting point of a capacitive reactance component and a resistance component is at a temp. higher than the maximum temp. for applying a sensor.

CONSTITUTION: The conductor wires 1 and 2 are provided in an organic molecular sensitive layer 3, and are used in the form of a parallel cable or a duplex winding. And a local organic molecule can be detected by the increase in a detecting current. The element is used by impressing an a.c., and the temp. of the intersecting point of a capacitive component and a resistance component can be selected by changing the applied frequency. An ion-conductive high molecular composition of which the base polymer is swollen by an externally functional molecule. And an internal winding wire 5 is wound on a core polyester yarn 4, an organic molecule sensing layer 6 is formed thereon, an external winding wire 7 is wound thereon, and a porous coating is covered as a housing 8. In this way, the detecting element of organic molecules is constituted. By heating the wire 5, the original state can be restored.