The skeletal isomerization of n-butene over γ-alumina fluorinated by impregnation was studies in a fixed-bed flow reactor. Acid characteristics of the catalysts were investigated through FT-IR analysis of adsorbed pyridine on the catalysts and its effect on the catalytic activity was examined. The experimental results showed the highest yield of isobutene at about 450℃. At higher temperatures than 450℃, catalysts were rapidly deactivated by coking and at lower temperatures the conversion of 1-butene was too low. It was found that Brönsted acidity was closely related to the yield for isobutene. 2wt%-fluorinated catalyst showed the maximum yield and selectivity for isobutene.