Insulator-to-metal transition of polyimide films can be performed by pyrolysis at high temperature as proposed by the authors. The maximum conductivity of the polyimide pyrolyzed at 950 degrees C for 0.5 h in a nitrogen atmosphere was measured to be 248 S/cm. The structure, electrical, and magnetic properties of the pyrolyzed polyimide depend on the pyrolytic conditions, such as pyrolytic temperature and time. The pyrolysis process consists of carbonization and graphitization processes, and a distinguishable pyrolytic temperature between them was estimated to be about 700 degrees C. In the carbonization process, an increase in conductivity with the pyrolytic temperature may be due to the formation of localized charge carriers. In the graphitization process, on the other hand, it is suggested that the delocalization of charge carriers is responsible for the high conductivity observed from pyrolytic temperature higher than 700 degrees C.