The intensity of light of a predetermined wavelength corresponding to the type of a protective tape joined to the surface of a semiconductor wafer is adjusted by a controller, and a holding stage for holding the semiconductor wafer is scanned rotationally. At this time, at a V notch portion for positioning formed in the semiconductor wafer, light is transmitted through the protective sheet covering the surface, which is received by a photoreception sensor. Based on the change in the reception amount of light in the photoreception sensor, the position of a detection site is specified.