Ion beam processing apparatus, electrode assembly, and method of cleaning electrode assembly

Provided is an ion beam processing apparatus including an ion generation chamber, a processing chamber, and electrodes to form an ion beam by extracting ions generated in the ion generation chamber to the processing chamber. The electrodes includes a first electrode disposed close to the ion generation chamber and provided with an ion passage hole to allow passage of the ions, and a second electrode disposed adjacent to the first electrode and closer to the processing chamber than the first electrode is, and provided with an ion passage hole to allow passage of the ions. The apparatus also includes a power unit which applies different electric potentials to the first electrode and the second electrode, respectively, so as to accelerate the ions generated by an ion generator in the ion generation chamber. A material of the first electrode is different from a material of the second electrode.