A light source emits light toward a semiconductor wafer, and a light receiving sensor detects light passing a peripheral edge of the semiconductor wafer. Each coordinates of the peripheral edge of the semiconductor wafer is obtained from a result of the detection. Further, a center of the semiconductor wafer is obtained from a group of the coordinates. Then, an illumination device emits light toward the peripheral edge of the semiconductor wafer and an optical camera detects light reflected from the peripheral edge of the semiconductor wafer. A position of a "V"-shaped notch formed on the peripheral edge of the semiconductor wafer is obtained from a result of the detection. A handling position of the semiconductor wafer is determined based on the center of the semiconductor wafer and the position of the "V"-shaped notch.