POLISHING METHOD AND POLISHING APPARATUS

A substrate polishing method capable of reducing an influence of variation in spectrum of reflected light from a substrate, such as a wafer, and determining an accurate film thickness is disclosed. The method includes: polishing a surface of a substrate by pressing the substrate against a polishing pad on a rotating polishing table; producing a spectrum of reflected light from the surface of the substrate each time the polishing table makes one rotation; creating a three-dimensional data containing a plurality of spectra arranged along polishing time; and determining a film thickness of the substrate based on the three-dimensional data.