Two-dimensionally organized CdS nanoparticle films were prepared with the use of Langmuir-Blodgett (LB) technique. Propanethiol-modified CdS nanoparticles were spread on water subphase, which contained 1,6-hexanedithiol as a cross-linking agent for binding the surface-modified CdS nanoparticles with each other. Surface pressure-area isotherms of CdS monoparticle layer taken after the cross-linking were largely different from those obtained without addition of 1,6-hexanedithiol in water subphase. After the cross-linking, the CdS monoparticle layer was transferred from the air-water interface to 1,6-hexanedithiol-modified gold substrate using the LB technique to give CdS monoparticulate film electrodes with dense packing of the nanoparticles on the gold substrate. By repeating the same techniques, the monoparticulate him was cumulated with desired amounts. The prepared CdS nanoparticle films showed n-type photosensitivities in proportion to the cumulation number of the monoparticle layers for less than five layers. Beyond that value, a saturation tendency of the photocurrent appeared.