Vapor-phase synthesis of aniline from phenol and ammonia was examined over various zeolites. Zeolite beta showed a high activity. Study of a theoretical interpretation of temperature-programmed desorption (TPD) of ammonia could correlate the catalytic activity with the acidic property. The activity for formation of aniline is almost proportional with the acid amount on each crystal phase of zeolite, and the turnover frequency of acid site seems to be ordered as FAU (faujasite)≈BEA (beta) > MFI (ZSM5) > MOR (mordenite). On the other hand, the acid strength was determined as FAU < BEA < MFI < MOR. Therefore, it is proven that the zeolite beta has a high activity because of its relatively weak acid strength.