A displacement amount detection apparatus comprising: a first resonant circuit that includes a first coil configured to be mounted to a movable member (12, 921); a second resonant circuit that includes a second coil that generates a magnetic field upon supply of an electric current and is configured to output a detection signal of a voltage level depending on a relative position of the second coil with respect to a position of the first coil, wherein the second coil faces the first coil; a pair of first and second equivalent circuits (70, 80), wherein: the first equivalent circuit is equivalent to the second resonant circuit in a case where the second resonant circuit is in a state in which a distance between the first coil and the second coil is infinite; and the second equivalent circuit is equivalent to the second resonant circuit in a case where the second resonant circuit is in a state in which the distance between the first coil and the second coil is zero; and a processor configured to: acquire a first output signal output from the first equivalent circuit when the electric current is supplied to the first equivalent circuit; acquire a second output signal output from the second equivalent circuit when the electric current is supplied to the second equivalent circuit; correct the detection signal based on the first output signal and the second output signal; and calculate, based on the corrected detection signal, a displacement amount of the movable member (12, 921). a first resonant circuit that includes a first coil configured to be mounted to a movable member (12, 921); a second resonant circuit that includes a second coil that generates a magnetic field upon supply of an electric current and is configured to output a detection signal of a voltage level depending on a relative position of the second coil with respect to a position of the first coil, wherein the second coil faces the first coil; a pair of first and second equivalent circuits (70, 80), wherein: the first equivalent circuit is equivalent to the second resonant circuit in a case where the second resonant circuit is in a state in which a distance between the first coil and the second coil is infinite; and the second equivalent circuit is equivalent to the second resonant circuit in a case where the second resonant circuit is in a state in which the distance between the first coil and the second coil is zero; and the first equivalent circuit is equivalent to the second resonant circuit in a case where the second resonant circuit is in a state in which a distance between the first coil and the second coil is infinite; and the second equivalent circuit is equivalent to the second resonant circuit in a case where the second resonant circuit is in a state in which the distance between the first coil and the second coil is zero; and a processor configured to: acquire a first output signal output from the first equivalent circuit when the electric current is supplied to the first equivalent circuit; acquire a second output signal output from the second equivalent circuit when the electric current is supplied to the second equivalent circuit; correct the detection signal based on the first output signal and the second output signal; and calculate, based on the corrected detection signal, a displacement amount of the movable member (12, 921). acquire a first output signal output from the first equivalent circuit when the electric current is supplied to the first equivalent circuit; acquire a second output signal output from the second equivalent circuit when the electric current is supplied to the second equivalent circuit; correct the detection signal based on the first output signal and the second output signal; and calculate, based on the corrected detection signal, a displacement amount of the movable member (12, 921).