The object of the invention is a device for the filtration of a complex fluid composition such as blood, characterized in that it comprises a base (12) with a bottom (18), a top (14) with a bottom (30), and a membrane (16) that is arranged between said base and said top so as to define a low chamber C1 and a high chamber C2, with an input tap (26) of the complex composition that is to be filtered emptying into the low chamber C1, an output tap (28) of the retentate with the means for adjustment of the flow rate emptying into this same low chamber C1, and an output tap (36, 36-1) of the high chamber C2, whereby this output tap (36, 36-1) of the permeate is subjected to negative pressure.
