An outer covering wall (26) and an inner covering wall (27), which are capable of surrounding a rotor (24), can be horizontally moved. A wafer carrier waiting portion (30) is disposed right below the rotor (24). A wafer holding member (41) included in a water lifter (40) moves into a wafer carrier (C) containing wafers (W) and mounted on a stage (31) (sliding table 32) included in the wafer carrier waiting portion (30), lifts up the wafers (W) and transfers the wafers (W) to the rotor (24). The outer covering wall (26) or the inner covering wall (27) surrounds the rotor (24) to define a processing chamber. The wafers (W) held on the rotor (24) are subjected to a cleaning process in the processing chamber.