Abstract: A device for holding an amount of magnetic fluid by means of a magnetic field inside a gap-shaped space located around a rotatable shaft, including a unit consisting of an annular pole piece whose inner circumferential plane is located at a relatively short distance from the shaft. The device has at least one annular permanent magnet for generating the magnetic field, whereby the magnetic fluid is kept inside the gap-shaped space between this unit and the shaft. The invention is characterized by the fact that the pole piece (3, 14) is located between two annular permanent magnets (1, 2; 12, 13), whereby the analogous poles of these magnets are directed at each other and the inner circumferential planes of the two magnets are located essential equidistance from the shaft (4, 11) in order to form, together with the shaft, two annular spaces which are located on both sides of an annular intermediate gap.