A filtering device (1) of the venous blood comprising at least a rigid box-shaped casing (2) defining a filtering chamber (3, 4), at least an internally hollow filtering element (5) arranged within the filtering chamber (3, 4) to delimit a pre-filtering chamber (3) and a post-filtering chamber (4), at least a supply pipe (7) of the blood to be filtered communicating with the pre-filtering chamber (3), where the box-shaped casing (2) is of the monolithic type and defines the supply pipe (7), the latter being arranged externally to the filtering chamber (3, 4) and comprising a first area (7a) defined at the upper portion of said casing (2) and connectable to a conveying line of the venous blood and a second area (7b) associated with the lower portion of said casing (2) and communicating with the pre-filtering chamber (3), the device (1) further comprising fractionation means (11) of the air bubbles arranged within the supply pipe (7).
