Hydroisomerization of benzene to methylcyclopentane has been studied using bifunctional catalysts consisting of Pt and an acidic Cs Salt Of H3PW12O40 The hydrogenation ability of Pt and the surface acidity (the amount of acid sites) of the bifunctional catalysts were key factors in determining the yield; the former is required for complete hydrogenation of benzene and the latter is parallel with the activity for skeletal isomerization of cyclohexane. However, for Pt-promoted acidic Cs salts, the hydrogenation ability tended to be suppressed as the amount of proton (Or the heteropoly anion) increased. As a result, 2 wt.%Pt-Cs2.5H0.5PW12O40 gave a high yield (51%) of methylcyclopentane at 473 K with 100% conversion of benzene. When 2 wt.%Pt was added to "Cs2.5H0.5PW12O40" which was prepared by impregnating Cs3PW12O40 With the aqueous solution of H3PW12O40, the higher yield of methylcyclopentane was also obtained.