A displacement sensor includes a first frame; a second frame; a first coil including a first voltage formed at the first frame applied to the first coil; a second coil formed at the first frame including a current of a second voltage flowing in the second coil corresponding to a voltage of the first frame if the first voltage is applied to the first coil; a conductor coupled to the second frame; and a detector for calculating a relative position between the first frame and the second frame by monitoring the second voltage. Further, a size of the second voltage is reduced if the second coil is moved closer to the conductor.