An amphiphilic iron porphyrin having four hexadecanoic acid chains on each face of the porphyrin was prepared and the catalytic epoxidation of linolenic acid with the heme-casted bilayer membranes was achieved in high regioselectivity at the terminal double bond of the substrate. The orientation of the porphyrin ring in the membrane was determined to be parallel to the aqueous-bilayer interface by means of ESR.