PURPOSE: To simultaneously examine a front surface and a rear face of a semiconductor wafer by providing a means for rotating a jig.

CONSTITUTION: He-Ne laser light 5 is applied from a light source 3 onto a surface of a wafer 2, and reflected or scattered light 5 is detected by a detector 4 to know whether or not a foreign material exists. At this time a wafer fixing jig 1 can rotate in a direction indicated by an arrow and both the front surface and a rear face of the wafer 2 can be directed to the light source 3. Therefore both the front surface and the rear face of the wafer 2 can be examined as for foreign materials at one time. It is also possible to prevent dust from occurring and from attaching to the rear face of the wafer 2.