Abstract: A filter device including an intermediate sleeve, an upper and a lower cap closing the upper and lower ends of the sleeve and cooperating with the sleeve to define an upper and a lower volume on opposite sides of an inner partition wall, and an inner tube disposed in the lower volume so as to extend from the partition wall and cooperating with the lower cap to define an inner space and an outer space which communicate with each other through a bottom space formed below the inner tube. The lower volume communicates with the upper volume through the inner space. The sleeve has an inlet port communicating with the outer space and receiving an incoming compressed air, and an outlet port communicating with the upper volume for discharging the air. The outer space is filled with a first packing. A porous structure is accommodated within the bottom space, for trapping droplets from the compressed air flowing through the first packing.