Thin films of a helical polysilane with chiral substituents were fabricated using a Langmuir-Blodgett (LB) method. The polarized absorption and photoluminescence spectra show the high anisotropy for the LB films with the polymer backbone lying in-plane along the dipping direction. The anisotropy of the lowest exciton absorption band can be enhanced by annealing the LB films. With use of the oriented LB film, we have revealed the one-dimensional exciton structures characteristic of polysilanes with helical conformations by measurements of electroabsorption spectra, compared with those of polysilanes of other conformations such as trans-planar and alternating trans-gauche backbone structures. The large binding energies of the lowest exciton are generic in the one-dimensional regular polysilanes, irrespective of the conformations.