To realize a wafer abnormality detection method which can detect an abnormality in a semiconductor wafer, such as wafer loaded in an adaptor being tilted.

A distance measuring device 21 for measuring a distance thereof from the outer peripheral part of a semiconductor wafer 2 loaded in an adaptor 1 is previously located at a constant position above the adaptor, the distance measuring device 21 measures the distance from the outer peripheral part of the semiconductor wafer, while the adaptor 1 is rotated. When the measured distance becomes a preset deciding value of smaller, it is decided that a tilt of the wafer exceeded its allowable range.