Abstract: The length in the direction of movement of a magnet is effectively used for position detection without using a gap of a stator, where the magnet moves, as a magnetic path. According to a proportion of the slider (110), having a magnet (111), that enters into a region where the slider is movable with a predetermined gap maintained between the stator (120) made from a magnetic body, a magnetism sensor (130) provided at a stator (120) detects the position of a slider (110). A magnetic flux leakage prevention member (140) prevents leakage of magnetic flux caused by that portion of the magnet (111) that has not entered in the region.

Abstract: Without utilizing a clearance between a moving magnet and a stator as a magnetic path, a length of the magnet in a moving direction is utilized in detection of the magnet effectively. In accordance with a percentage of a slider 110 having the magnet 111 that enters a movable area of the slider 100 while keeping a predetermined clearance to the stator 120 consisting of a magnetic body, a magnetically-sensitive sensor 130 provided in the stator 120 detects a position of the slider 110. A magnetic flux leakproof member 140 prevents magnetic flux generated in a part of the magnet 111 that does not enter the area from leaking out to the stator 120.