A fluid filtration device contains a processing tank, a driving unit disposed outside the processing tank, a water pipe and a filtering unit. The processing tank is formed by plural substrate units arranged around the processing tank, each substrate unit has plural plate members connected together and formed on equal proportion, each plate member has an external surface and at least one circularly recessed portion, and on two connecting edges of any two adjacent plate members is defined a connector. The water pipe is connected with the driving unit and includes a peripheral wall, a plurality of apertures, and plural retaining protrusions. The filtering unit includes a plurality of filtration bags and plural guiding disks, each filtration bag has a first central pore, and each guiding disk has a body, a second central pore, and a plurality of coupling recesses.