Abstract: A motor having a magnetic oil seal structure comprises a bearing sleeve, an oil-retaining bearing, a coil set, a rotor, a fastening ring, a magnet and magnetic fluid. The bearing sleeve has a receiving space. The oil-retaining bearing is received in the receiving space. The coil set is slipped outside the bearing sleeve. The rotor has an axis rotatably inserted into an axial hole of the oil-retaining bearing. The fastening ring is fastened on the axis and located above the oil-retaining bearing. The magnet is above the fastening ring. The magnetic fluid is provided between the magnet and the axis of the rotor. Magnetic force between the magnetic fluid and the magnet lets the magnetic fluid be tightly absorbed in the gap between the axis and the magnet to form a magnetic oil seal circuit, hence preventing the oil-retaining bearing from losing oil and greatly increasing its lifetime of use.