Thermal depolarization current (TDC) of polypyromellitimide film was measured in order to obtain knowledge of the charging and discharging mechanisms of carriers in polypyromellitimide. Two peaks are observed at 173 (&agr;) and 50 °C (&bgr;) in the dried film. The &bgr; peak attributed to dipole orientation polarization is probably associated with residual reactive groups in polypyromellitimide. The &agr; peak shows nonlinear dependence on polarization electric fieldEp. The sign of the current changes with small collecting electric fieldEcwhich is applied during the TDC measurement. The &agr; peak depends on electrode materials. The &agr; peak is considered to be attributed to space‐charge polarization due to trapping of electrons injected from the cathode in the vicinity of the polymer film surface. The nonlinearEpdependence of the &agr; peak can be described by a two‐site hopping model.