We obtained kinetics data on steam reforming of butane and calculated the appropriate reactor size based on the kinetics data. Using commercial Ni and Ru catalysts, steam reforming reactions of butane were performed while changing the reaction temperature and partial pressure of reactants. After comparing the power law model and the Langmuir-Hinshelwood model by using the kinetics data obtained from the experiment, it is revealed that the reaction rate could be determined by both models in the reforming reaction of butane over commercial Ni and Ru catalysts. Also, calculation of the steam reforming reactor size using a PRO/II simulation with a kinetic model equation showed that the reactor size using the Ni catalyst is smaller than that with the Ru catalyst to obtain the same conversion.