Amphiphilic NaY zeolite particles were prepared by a partial modification of the external surface of NaY with alkylsilyl groups. When the particles were added to a mixture of aqueous hydrogen peroxide and normal alkene, they were feasibly located just at the liquid-liquid phase boundary and efficiently catalyzed epoxidation of the alkenes even without stirring. Fluorescence microscopic observation of these particles selectively modified with fluorescent dye revealed that each particle has a bimodal amphiphilic surface structure; one side of the external surface is hydrophilic and the other is hydrophobic.