Effects of nanofiller loading on the carrier transport and molecular motion 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, a relaxation due to dipolar orientation, and ß relaxation due to rotation of amide groups bonded with water molecules, in addition to interfacial polarization at crystalline/ amorphous boundaries. The enhancement of dielectric constant and that of loss factor due to abundance of mobile charge carriers are suppressed by the nanofiller loading. These results suggest that carrier transport is suppressed by the nanofillers. Furthermore, it was found that relaxation time becomes longer by the mica nanofiller loading both for the dipolar orientation and for the rotation of amide groups. Molecular motion is considered to be restricted in nano-composites, which indicates a strong interaction between the resin and filler.