A method for cleaning a filtering membrane, contaminated by contaminants including inorganic and organic materials during a fluid-filtering process, is disclosed, the method comprises cleaning the filtering membrane by using a first cleaning solution of pH 6˜9 so as to remove the organic material from the filtering membrane; and cleaning the filtering membrane by using a second acid cleaning solution so as to remove the inorganic material from the filtering membrane, wherein the cleaning method of the present invention uses the first cleaning solution having pH 6˜9 instead of a strong-alkaline cleaning solution so as to prevent the filtering membrane from being damaged, and also uses the cleaning solution maintained at a relatively low temperature instead of hot water so as to improve economical efficiency by reduction of energy consumption.