A membrane electrode assembly includes a cation exchange membrane electrode assembly and an anion exchange membrane electrode assembly. The cation exchange membrane includes a cation exchange membrane, a first cathode electrode disposed on the cation exchange membrane, and a first anode electrode disposed under the cation exchange membrane. The anion exchange membrane electrode assembly includes an anion exchange membrane, a second cathode electrode disposed on the anion exchange membrane, and a second anode electrode disposed under the anion exchange membrane. The cation exchange membrane and the anion exchange membrane partially contact each other, and the first cathode electrode, the first anode electrode, the second cathode electrode, and the second anode electrode do not contact one another.