Abstract: A wafer detection apparatus for detecting wafers received in stages formed in a wafer carrier is provided which includes a light emitting section arranged movably in the thickness direction of wafers which are received in the stages along the peripheral wall of the wafer carrier, for emitting detection light toward the position of each stage for receiving a wafer, a light receiving section arranged movably in the thickness direction of the wafers for receiving the detection light emitted from the light emitting section and outputting a received light amount, a drive mechanism for moving the light emitting section and the light receiving section together relative to the wafer carrier, a storage device supplied with an input signal from the light receiving section and storing a history of change of the received light amount, and determining means for determining whether a wafer is received in each stage of the wafer carrier or not based on a received light amount curve indicative of change of the received light