This paper describes novel Au/NaY catalytic membranes for preferential oxidation of CO (CO-PROX) in an H₂-rich gas. NaY zeolite membranes with a high CO₂/N₂ separation factor were loaded with nanosized Au particles using an ion-exchanged method. X-ray diffraction analyses showed that the structure of the NaY zeolite was not damaged by the ion exchange process. CO-PROX experiments showed that the catalytic membranes had excellent catalytic performance for selective oxidation of CO. The CO/H₂ molar ratio on the permeate side decreased with increasing operating temperature in the range of 80-200℃. At 200℃, almost no CO was detected from the permeate stream of a catalytic membrane with the feed containing 0.67% CO, 1.33% O₂, 32.67% H₂, and He in balance. Thus, these Au/NaY catalytic membranes show a promise for CO removal from hydrogen fuels.