A low resistance air filter device comprises a tubular case (2) for at least a filtering element (3) fixed to a lower opening (9) of the case (2). This latter case is provided, at its opposite upper opening (10), of outlet means (8) provided with an outflow opening (7) for the air. The outlet means (8), at the outflow opening (7), are provided of a tubular body protruding toward inside said tubular case (2) and connect in flow communication the inside volume of the tubular case with the outflow opening (7) the same.