A filtering method including the steps of preparing a water purifying apparatus 1 with a cell structure 2 having units for constituting cell structure 4, and a cap portion 3, and making raw water flow into cells 10 from one end, and filtered by a partition walls 9 to take out filtrate water from the side of an outer peripheral surface 8. The cell structure 2 is so constructed that the ratio of maximum value to minimum value in water permeability among the partition walls 9 provided therein is within a range from of 110 to 300% in terms of percentage, and the cells 10 located on the side of an outer periphery 7 of the cell structure 2 have a greater water permeability.