Catalytic oxidation activities of carbon monoxide on faujasite zeolite, CuHY and CuNaY, were measured by controlling cupric ion exchange level in the zeolite. A significant increase in the oxidation activity was observed to occur at 42 % cupric ion exchange level on CuHY, but this was not the case with CuNaY. Nevertheless, in the latter kinetics, there appeared a minimum oxidation activity at the same ion exchange level when temperature was raised up to 350 ℃. In the cupric ion exchange level below 42 % and the temperature range lower than 270 ℃ the activation energy of the kinetics on CuHY and CuNaY showed 6 and 20 Kcal/mole respectively. However, as the cupric ion exchange level increased beyond 42 % such a distinguishable difference in activation energy between two solids disappeared giving the value of 12 Kcal/mole. It is probably due to only the effect of cupric ion under these circumstances. In the temperature range higher than 270 ℃ the activation energy on CuHY could not be measured due to complete conversion of reactants but on CuNaY revealed the same value of 20 Kcal/mole as that observed in the lower temperature range, independent of the cupric ion exchange level. This implies that the influence of sodium ion became prevaillng over the cupric ion.