A processing end point detection method detects a timing of a processing end point (e.g., polishing stop, changing of polishing conditions) by calculating a characteristic value of a surface of a workpiece (an object of polishing) such as a substrate. This method includes producing a spectral waveform indicating a relationship between reflection intensities and wavelengths at a processing end point, with use of a reference workpiece or simulation calculation, based on the spectral waveform, selecting wavelengths of a local maximum value and a local minimum value of the reflection intensities, calculating the characteristic value with respect to a surface, to be processed, from reflection intensities at the selected wavelengths, setting a distinctive point of time variation of the characteristic value at a processing end point of the workpiece as the processing end point, and detecting the processing end point of the workpiece by detecting the distinctive point during processing of the workpiece.