The true performance of field-effect transistors with spin-coated organic–inorganic perovskite (C6H5C2H4NH3)2SnI4 semiconductor layers remains unknown because of the presence of contact resistance (RC). To evaluate the intrinsic carrier mobility (μ), we fabricated perovskite transistors with large channel lengths (L). The field-effect μ gradually increased with increasing L and then became constant in the large-L region, because of the reduced contribution of RC relative to the total resistance. The intrinsic μ values estimated from this region reached 26 and 4.8 cm2 V−1 s−1 for holes and electrons, respectively, which are the highest ever reported in any perovskite transistor.