Effects of nanofiller loading on the molecular motion and carrier transport in polyamide-6/mica nanocomposites were discussed by analyzing their complex permittivity spectra. As a result, the following four dielectric polarization processes were observed; space charge polarization, interfacial polarization at crystalline/amorphous boundaries, alpha relaxation due to dipolar orientation, and beta relaxation due to rotation of amide groups bonded with water molecules. The enhancement of dielectric constant and that of loss factor due to abundance of mobile charge carriers are suppressed by the nanofiller loading. Furthermore, it was found that the relaxation time becomes longer by the mica nanofiller loading both for the dipolar orientation and for the rotation of amide groups. These results suggest that molecular motion that assists carrier transport is suppressed in nanocomposites, which indicates a strong interaction between the resin and filler.