There is provided a method for driving a member provided in a processing chamber. The method includes irradiating to the member measurement light having a wavelength that penetrates the member, detecting intensity distribution of reflected light based on reflected light from an upper surface of the member and reflected light from a bottom surface of the member, calculating an optical path difference by applying Fourier transform to a spectrum indicating the intensity distribution, and determining a driving amount of the member based on the optical path difference. The method further includes driving the member based on the determined driving amount.