Methanol decomposition (CH3OH→2H2+CO) was performed over thin foils of intermetallic compound Ni3Al. It was found that the methanol decomposition was effectively catalyzed over the Ni3Al foils in the temperature range of 440-520℃. The rate of H2 production rapidly increased during the initial several hours of reaction at 520℃, and then stabilized at a high value (42 mol/hr-㎡) during the subsequent reaction. Furthermore, the Ni3Al foils showed almost no loss of activity through the whole range of reaction time, displaying an excellent catalytic stability. Surface analyses by BET, SEM, XRD, and TEM revealed that porous carbon nanofibers containing fine Ni particles formed spontaneously on the NisAl foils during the reaction at 440-520℃. These surface products, i.e., fine Ni particles and carbon nanofibers, are supposed to serve as a catalyst and a catalyst support for the methanol decomposition, respectively.