A polishing apparatus is disclosed, comprising a polishing section configured to polish a substrate, wherein the substrate has a plurality of laminating films including an upper layer and a lower layer; a measurement section configured to measure a thickness of a film formed on the substrate; an interface configured to input a desired thickness of a film formed on a substrate to be polished; an arithmetic unit operable to calculate a polishing rate and an optimal polishing time based on the polishing rate data and the desired thickness by using a weighted average method which weights the polishing rate data on a lately polished substrate. The invention also discloses a polishing method.