PURPOSE: To provide the excellent method for washing carbon material parts to improve the electrode performance of a fuel cell and prolong the lifetime by preventing the burning at the time of burning catalyzer of a ribbed electrode of a fuel cell, and improving the gas permeability of the ribbed electrode to enable the even distribution of the electrolyte such as phosphoric acid.

CONSTITUTION: Ozonized gas, which includes the ozone generated by an ozone generator 11, is fed to a diffusion cylinder 13 provided in the bottom of an ozone absorbing tower 12, and is poured as fine bubble in the water filled inside of the ozone absorbing tower 12 to obtain the ozone included water. The ozone included water inside of the ozone absorbing tower 12 is fed by a liquid feeding pump 14, and is blown from a nozzle 15 to the surface of the ribbed electrode 2 to contact to the ribbed electrode 2. The structure, in which the ozone absorbing tower 12 is omitted, or the structure, in which the ribbed electrode 2 is impregnated with the ozone included water, is possible.