The potentiometer of the present invention includes at least a pair of giant magnetoresistive effect elements, in which the giant magnetoresistive effect elements to be paired are formed on a substrate in a state that the elements are connected mutually electrically with the orientations of magnetization axes of the pinned magnetic layers facing 180° opposite each other, and a magnetic coding member is rotatably provided to face the giant magnetoresistive effect elements on the substrate, the magnetic coding member is disposed in such a manner that the center of rotation of the magnetic coding member passes through an intermediate position of the giant magnetoresistive effect elements to be paired, and the magnetic coding member has at least two magnetic poles formed along the direction of rotation of itself.