Embodiments of this application discloses a substrate processing apparatus comprising: a vacuum transfer module having a vacuum transfer space and an opening; a wall unit attached to the opening and including a first gate valve and a second gate valve; a substrate processing module attached to the wall unit and having a substrate processing space communicating with the vacuum transfer space via the first gate valve; and a ring stocker attached to the wall unit and having a storage space for storing at least one annular member used in a plasma processing module. Moreover, the apparatus further includes a transfer mechanism disposed in the vacuum transfer space and transfers a substrate between the vacuum transfer space and the substrate processing space through the first gate valve and also transfers at least one annular member between the vacuum transfer space and the storage space via the second gate valve.