In operation S416, with reference to FIG. 1, the wafer in the buffer chamber 130 is transferred to the load lock chamber 120 through the valve V2 by the robot blade 132 of the robot 131 of the buffer chamber 130. Before transferring the wafer, the valves V1-V2 are closed, and the environment in the load lock chamber is kept in the second environment since the valves V1-V2 are kept closed after the operation S404. Then, after the valve V2 is open, the wafer is transferred from the buffer chamber 130 to the load lock chamber 120. For illustration in FIG. 1, the wafer is transferred from the position D or the position E in the buffer chamber 130 to the position B by the robot blade 132 of the robot 131 of the buffer chamber 130. After the wafer is transferred to the load lock chamber 120, the valve V2 is close in order to isolate the environment between the load lock chamber 120 and the buffer chamber 130.