Abstract: This magnetic screw device comprises a screw shaft made of magnetic material and having thread ridges formed on the outer peripheral surface thereof, and a nut body fitted on the screw shaft with a clearance defined therebetween. The nut body comprises a magnetic sleeve having a smoothly finished inner peripheral surface and substantially concentric with the screw shaft, and guide rings disposed at the opposite ends of the magnetic sleeve as viewed in the thrust direction, and a housing for holding the magnetic sleeve and guide rings. The magnetic sleeve is helically magnetized on its inner peripheral surface with magnetic poles opposed to the thread ridges of the screw shaft, so that when the screw shaft is rotated, the nut body 7 is linearly moved by the magnetic action.