Considering the basic concepts of P‐type and N‐type originated from inorganic semiconductors, it has been deduced in this report that the non‐doped polymer semiconductors should be ambipolar materials. Thus, the carrier dynamics of hole‐only and electron‐only devices of poly(N‐vinylcarbazole) (PVK) are researched through impedance spectroscopy. The results show that the hole and electron transports both possess high dispersion with parameter of 0.1–0.2 and 0.1, respectively. In addition, the hole and electron mobilities under different electric field are basically in the same order of magnitude, which shows that PVK is one intrinsically ambipolar polymer semiconductor although it is traditionally thought to “P‐type.” Finally, the abnormal negative slope phenomenon of transferring curve is analyzed, which is ascribed to the energy relaxation through vibration in polymer segment. This paper uses impedance spectroscopy to study the carrier dynamics of non‐doped “P‐type” poly(N‐vinylcarbazole). The hole and electron mobilities of poly(N‐vinylcarbazole) are almost same to each other under various film thickness conditions. In addition, the mobilities are negatively dependent on the electric field, which is attributed to the energy relaxation through vibration of polymer segment.