Permeability coefficients, apparent diffusion coefficients, and apparent solubility coefficients of n-butane and l-butene gases across anhydrous sulfonated and carboxylated polyperfluorocarbon-type cation exchange membranes which have different counterions of Na+, Ag+, Co2+, and Ni2+ were investigated at 25 degrees C. Prior to the n-butane and l-butene gas permeability measurements, O-2 gas permeabilities were measured. From the results, it was shown that those membranes appeared to dense membranes. In each membrane, the permeability of l-butene was higher than that of n-butane. In comparison with the same counterion membranes, the sulfonated membrane had higher permeability than the carboxylated membrane for both gases;The Ag+-form sulfonated membrane exhibited the highest permeability coefficient for l-butene and the ideal separation factor of 1-butene/n-butane was 10.3. This is caused by the high solubility of l-butene gas. From the calculated result using the MO method, it was shown that the interaction between the olefin and metal ions was weakened by the influence of a charged group. Therefore, the affinity between the olefin and Co2+ Or Ni2+ did not function in the membrane as expected because of the divalent ions. This is the reason why the solubility coefficients of Co2+- and Ni2+-form membranes were smaller than those of the Ag+-form membrane,