This invention provides a wafer processing method comprising a process of irradiating a wafer to be processed placed on the upper surface of a sample table arranged in a processing chamber with light or electromagnetic waves to heat and remove a compound layer of a film layer that is preliminarily formed on the upper surface of the film layer of the upper surface of the wafer, wherein in the process, by receiving the light or electromagnetic waves reflected by the upper surface of the wafer, a signal indicating a temporal change in intensity using the wavelength of the light or electromagnetic waves as a parameter is corrected using information of the intensity of the light or electromagnetic waves detected by receiving the light or electromagnetic waves at a position on the circumferential side of the upper surface of the sample table.