Aligned self-assembled fibers have been obtained for a phenylbithiophene derivative with a laterally fluorinated phenylene group by the application of electric fields. These fibrous aggregates exhibit photoconductive properties due to the stacking of the π-conjugated moiety. In contrast, a phenylbithiophene derivative without fluoro substituents forms unaligned fibers under electric fields. The dielectric anisotropy of the fluorinated molecule plays a key role in the alignment of photoconductive fibrous aggregates.