The effect of hydrogen spillover over Pd/SiO2 + USY on pyridine chemisorbed on acid sites of USY zeolite was investigated. According to FTIR measurement, pyridine adsorbed on Lewis acid sites migrated to Bronsted acid sites under hydrogen-flowing atmosphere. The rate of migration was drastically promoted by physically mixed Pd/SiO2 catalysts. This suggests that spilt-over hydrogen enhance the migration of pyridine adsorbed on Lewis acid sites.