Magnetic screw device

A magnetic screw device comprising a screw shaft made of magnetic material and having ridges formed on the outer peripheral surface thereof, and a nut body fitted on the screw shaft with a clearance defined therebetween, said nut body having magnetic poles disposed on the inner periphery thereof, said magnetic screw device further comprising on the nut body side, a magnetic sleeve having a smoothly finished inner peripheral surface disposed substantially concentrically with said screw shaft, the inner peripheral surface of said magnetic sleeve being helically magnetized with said magnetic poles in opposed relation to the ridges of said screw shaft, and guide rings disposed on and attached to the opposite sides of said nut body as viewed in the thrust direction for holding said screw shaft substantially concentrically with said magnetic sleeve to slidably guide said screw shaft, wherein said nut body comprises the magnetic sleeve fitted on said screw shaft with a clearance defined therebetween, said guide rings disposed at the opposite ends of said magnetic sleeve as viewed in the thrust direction, and a housing for holding from the outer periphery side said magnetic sleeve and guide rings.