Provided is a movement distance measurement apparatus for confirming the operating state of a power transmission device for automobiles, which has removed the effect of temperature, and the movement distance measurement apparatus for confirming the operating state of a power transmission device for automobiles, which has removed the effect of temperature, is configured to measure the movement distance T of the detection target object 20 using a resonance circuit including the sensing coil by using changes in the resonance frequency of the resonance circuit and changes in the output voltage of the resonance circuit according to changes in the distance between the detection target object 20 and the sensing coil, and to be provided with a diode voltage detection unit that separately detects diode voltage included in the output value of the resonance circuit not to be affected by temperature change by removing the diode voltage.

A backlash measuring method is provided for measuring backlash at a plurality of different times. The backlash measuring method includes: a rotation amount calculating step of braking a ring gear relative to a second portion while contact between a target tooth and the ring gear achieved in a contacting step is maintained, causing a target pinion to rotate toward a second side in a rotation direction opposite to the first side with a driving force less than a braking force applied to brake the ring gear relative to the second portion until the target tooth touches the ring gear at a tooth surface facing the second side, and calculating an amount of rotation of the target pinion; and a measuring step of measuring backlash between the ring gear and the target pinion based on the amount of rotation of the target pinion calculated in the rotation amount calculating step.