To reduce the size of a direct actuator, having a slide position detector in a direction perpendicular to a shat, without the need for providing a magnetic marker on the entire surface of a guide rail and without the need for providing a detecting coil, so as to surround the rail as well, and to protect the pattern of the magnetic marker from the scraper of a direct actuator unit, by providing a protective sheet on the front surface side of the magnetic marker.

The direct actuator, having the slide position detector comprises the strip-like magnetic marker 12 provided on the upper surface 10 of the guide rail 4, and a plurality of detecting coils 14 provided on the upper part of the direct actuator unit 6, so as to face to the magnetic marker 12. The marker 12 is obtained by covering the pattern, having a cutout 32 provided on a copper plate with the protective sheet, such as a stainless steel or the like.