WATER PURIFICATION SYSTEM AND WATER PURIFICATION METHOD

A water purification system 1 comprises: a flocculation unit 2 for adding a flocculant to raw water; a first filtration unit 3 having a first filter material layer 31 that includes a plurality of first filter materials 35, the flocculation-treated water that has passed through the flocculation unit 2 being passed through the first filtration unit 3 as an upward flow; and a second filtration unit 4 having a second filter material layer 41 that includes a plurality of second filter materials 45, the filtered water that has passed through the first filtration unit 3 being passed through the second filtration unit 4 as a downward flow. The porosity of the first filter material layer 31 is set to 85-91% inclusive, and the porosity of the second filter material layer 41 is set to 92-96% inclusive.