Abstract: A magnetic detection unit includes: a first magnet configured to generate a first magnetic field; a second magnet arranged in parallel with the first magnet, the second magnet being configured to generate a second magnetic field in a direction opposite to a direction of the first magnetic field; and a hall element having a magnetic-flux detection surface, the hall element being configured to output a signal corresponding to a magnetic flux density passing through the magnetic-flux detection surface. The hall element is arranged at a position where a direction of a magnetic flux in a synthetic magnetic field of the first magnetic field and the second magnetic field is parallel to the magnetic-flux detection surface.

Abstract: Stroke detectors include magnetic detectors that output signals in accordance with magnetic fields that are changed by scales. The magnetic detectors include first hall elements that detect change in magnetic flux, first magnets that generate first magnetic field, and second magnets that generate the second magnetic field. The first magnets and the second magnets are arranged such that the first magnetic field and the second magnetic field are cancelled out in the first hall elements.