We present the spot size and incident angle dependence of filtering characteristics of dielectric multilayer thin-film filters. Experimental results on amplitude responses and dispersion characteristics of narrow pass-band (50GHz) SiO₂/Ta₂O₅ filters are presented, which are in good agreement with theory. Although noticeable deterioration on amplitude filter responses has been seen, the chromatic dispersion is reduced with decreasing the spot size of input light.