Abstract: A fractional filtration apparatus, used for obtaining cutting oils fractionally cleaned by using one filtration apparatus so as to reuse the separated cutting oils in accordance with the types of machining operations, includes a plurality of liquid tanks for fractionally storing the cleaned cutting oils, a filtration target cutting oil storage tank for temporarily storing a filtration target cutting oil charged through a charge port, rotatably driven filtration drums, dividing the liquid level of the cutting oil and being pivotal in the filtration target cutting oil storage tank, each drum having a side-surface opening in at least one surface thereof in order to let a filtered cleaned cutting oil flow into the cutting oil tanks, and each drum being provided with filters of different mesh sizes, injection nozzles for reversely washing the filters provided on the outer circumferential surfaces of the filtration drums, and dip-up members, disposed at a predetermined intervals, for continuously conveying the cutt