A plurality of layers of flat coils are stacked and connected in series with each other to form a single coil pole, and the coil pole is energized by an A.C. signal. Magnetism-responsive member, provided to be opposed to the coil pole in a non-contact manner, is displaced relative to the coil pole, so that correspondency, to the coil section, of the magnetism-responsive member varies in response to variation in the relative position and thus impedance variation occurs in the coil pole. Position detection signal is provided on the basis of an output signal, responsive to the impedance variation, taken out from the coil pole.