A simplified parallel plate model for micropore structure of active carbon is studied by summing the permutations of the set of n (the integer, 7 less than or equal to n less than or equal to 10) plane surfaces with the value of D-PDS - 1 (= D-DR - 1), where D-PSD is the fractal dimension defined in the pore-size distribution function dV/dL proportional to L(2-D), dV being the adsorption volume between L and L + dL, in the micropore range (L less than or equal to 2 nm) and D-DR is the fractal dimension determined using the Dubinin-Radushkevich (DR) micropore volume V-0 as a function of the adsorbate molar volume upsilon, i.e., V-0 proportional to upsilon((3-D)/3). Comparison of the micropore-size distribution histograms of the parallel plate model with those curves of the pore-size distribution function showed that the surface fractal dimension D-S can be approximated by D-DR - 1 or D-PSD - 1. From the results, the surface fractal dimension D-S of micropore walls of active carbon is further confirmed to be D-S < 2 (ca. 1.9) in the parallel plate model.