Poly(4-vinylpyridine) resin beads with 3%, 5%, and 10% crosslinkings were prepa- red, and then the quaternization by alkyl halides was investigated. The quaternization rate de- creased with increasing the degree of crosslinking and the size of alkyl halide, however, increased with increasing the dielectric constant of solvent. Particularly the reaction rate steeply decreased as the quaternization more or less proceeded and this phenomenon could be interpreted through the proposed model.