A hydrogen purifier includes an electrolyte membrane including a proton conductive polymer, an anode having an anode catalyst layer disposed on one side of the electrolyte membrane, a cathode having a cathode catalyst layer disposed on the other side of the electrolyte membrane, a separator which has a fluid channel and through which carbon monoxide, hydrogen and oxygen are supplied to the anode, and a power supply that energizes the anode and the cathode, the anode catalyst layer including Pt, the cathode catalyst layer including Pt and Ru.