A magnetic filter for separating ferromagnetic particles from a fluid. The filter includes a filter container having an inlet, outlet, and inner space wherein an annular filter element is located. A magnetic-field generating device is surrounded by the annular filter element, and is adapted to magnetize the filter element. A fluid to be filtered is allowed to enter the filter from the inlet, and ferromagnetic particles in suspension in the fluid, when passing the filter element, are attracted thereby. The purified fluid is allowed to flow out of the filter through the outlet.