Thermally stimulated currents (TSC) have been measured in undoped polyaniline film at various heating rates. Main TSC peak measured around 170K at the heating rate of 0.033K/s was separated to three single TSC curves by the proposed auto-separation method. The separated main peak evaluated as about 0.14 eV did not depend on collecting fields, but increased considerably by increasing heating rates. These results suggest the possibility of sure structual change of molecular arrangements.