Mn-porphyrin cages confining ca. 1.4-1.5 nm Pd and Au clusters (1a and 2a) showed high catalytic turnover numbers rather than simple monomeric porphyrin complex (3a) in styrene epoxidation by iodosobenzene. Absorption spectroscopic studies indicated that the accumulation of inactive species is efficiently suppressed when the cage catalysts la and 2a were employed.