A fluid treatment method includes the steps of forming a ring lamination by laminating a plurality of filtering rings with contact surfaces facing each other in a laminating direction; providing at least portions of the filtering rings with a contact surface roughness (Ra) in a range of about 0.01 .mu.m to 20 .mu.m; pressing the ring lamination under a contact surface pressure (p) within a range from 0 to 177 kg/cm.sup.2 in the laminating direction of the filtering rings to cause the contact surfaces to closely adhere to each other; directing an object fluid into gaps formed by contact surfaces of neighboring filtering rings of the ring lamination; and dividing the object fluid into a first separated fraction and a second separated fraction for separation. An apparatus for carrying out the method includes a ring lamination, a housing therefor, a ring press for acting on the ring lamination under a prescribed pressure, an object fluid source, and a pressure source for impressing a prescribed pressure on the object fluid.