Abstract: An adapter is provided which is used when a process for a small-diameter semiconductor substrate (small substrate) is performed by using a semiconductor manufacturing apparatus for large-diameter silicon substrates. The small substrate is attached to an adapter plate that compensates for differences in size, so that the small substrate is prevented from falling even when the small substrate is in a vertical or inverted direction. To process the small substrate with the semiconductor manufacturing apparatus for large-diameter silicon substrates, an opening 10 is formed in a transferring base portion 1, which is formed of a large-diameter silicon substrate, and a polyimide film 2 is attached to the rear surface of the transferring base portion 1, so that the small substrate can be retained by a vacuum chuck or an electrostatic chuck.