Permeability coefficients, apparent diffusion coefficients, and apparent solubility coefficients ofn-butane and 1-butene gases across anhydrous sulfonated and carboxylated polyperfluorocarbon-type cation exchange membranes which have different counterions of Na + , Ag + , Co 2+ , and Ni 2+ were investigated at 25°C. Prior to then-butane and 1-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 1-butene was higher than that ofn-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 1-butene and the ideal separation factor of 1-butene/n-butane was 10.3. This is caused by the high solubility of 1-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 Co 2+ or Ni 2+ did not function in the membrane as expected because of the divalent ions. This is the reason why the solubility coefficients of Co 2+ - and Ni 2+ -form membranes were smaller than those of the Ag + -form membrane.