A positioning jig has a circular part with a diameter that is identical with a diameter of a semiconductor wafer and knock-pins for connecting a periphery of base plate around an opening in a base plate of a conveying tool for a semiconductor wafer. These knock-pins are respectively provided in four blades protruded from predetermined positions of the circular portion at least three directions. When adjusting the projection positions of supporting plates, the knock-pins are fitted into the opening of the base plate of the conveying tool for the semiconductor wafer. The supporting plates moves so that the knock-pins come into contact with an outer edge of the circular part of the prepared positioning jig. The adjusted supporting plates are then fixed on the base plate. The semiconductor wafer is mounted on the adjusted and fixed supporting plates so that the semiconductor wafer is positioned.