Blazars are highly variable AGNs emitting radiation at all wavelengths from radio to gamma-rays. They have strong relativistic jets aligned with the observer”Ēs line of sight and are apparently bright due to relativistic beaming. Polarized radiation is one piece of evidence of synchrotron origin in low energies and it also varies drastically. Thus, the polarization is of interest for understanding the origin, confinement, and propagation of jets, due to the dependence of the polarization on the jet”Ēs magnetic field structure. We performed polarimetric observations of AGN jets with Kanata optical telescope in several types of AGNs with various timescales (from minute to year) to study of structures and emission regions of relativistic jets. We search for a basic relation between gamma-ray properties and optical flux and polarization with a systematic study of 45 AGNs to investigate the mechanisms of variability. We found a significant correlation between the maximum degree of optical linear polarization and the gamma-ray luminosity, and it can be explained by a spine-sheath model and systematic difference in the intrinsic alignment of magnetic fields in relativistic jets.