We have applied the spin dynamics technique to conducting polymers, in particular, with the ESR method, and investigated microscopic transport properties in a quasi-one-dimensional (Q1D) polymer chain. This technique is a unique method for obtaining microscopic information on intrinsic transport properties, because macroscopic resistivity is mainly limited by electrical properties of interfacial regions between microcrystals. In this article, the principles and applications of this method will be reviewed in detail. The difference between ESR applied here and H-1 NMR will also be discussed, and each characteristic feature will be stressed.