PURPOSE: To change the alignment of semiconductor wafers in a short time by reading a symbol representing the number of a wafer on a conveying passage, assigning it to any of a buffer wafer cassette according to the type of the symbol, and then sequentially containing in a predetermined order in a wafer cassette of containing side.

CONSTITUTION: A semiconductor wafer 6 which passes a wafer number reader 3 clarifies a lot to which the wafer 6 belongs from the read wafer number 12. Thus, an apparatus control circuit drives a semiconductor wafer main conveyor belt 5 and a semiconductor wafer sub conveyor belt 7 to contain the wafer 6 in a buffer wafer cassette 4 assigned in advance for the detected lot. Then, the content of the cassette 4 is contained in a predetermined order in a semiconductor wafer cassette 2 of containing side by driving the belts 5, 7. When the contents of all the cassettes are contained in the cassette 2, the content of the cassette 2 is separated at every lot.