There are provided a method for obtaining a distance between a base portion of an electrostatic chuck and a back surface of a target object and a method for neutralizing the electrostatic chuck based on the obtained distance. The electrostatic chuck has an upper surface including the base portion and a plurality of convex portions projecting from the base portion. The target object is mounted on apexes of the convex portions of the electrostatic chuck such that the back surface is in contact with the apexes. By processing a first wavelength spectrum output from a spectroscope based on reflected light of light emitted from a light source, a distance between the back surface of the target object and the base portion of the electrostatic chuck is calculated. Based on the calculated distance, a voltage is applied to the electrostatic chuck to neutralize the electrostatic chuck.