In aerobic oxidation of benzyl alcohols to benzaldehydes under continuous flow conditions for aerobic oxidation, using the honeycomb reactor gave a higher reaction rate than the standard tube reactor or the tube reactor with the static mixer. The honeycomb reactor is a promising device for streamlining aerobic oxidation under continuous flow conditions with process safety. The high gas-liquid contact efficiency using the honeycomb reactor can also be applied to other gas-liquid flow reaction systems.