An upper member is disposed at an upper portion within a processing chamber. A ceiling member forms a ceiling of the processing chamber, and is provided with a through hole at a facing surface thereof which faces the upper member. A supporting member supports the upper member with a first end thereof located inside the processing chamber by being inserted through the through hole and slid within the through hole. An accommodation member accommodates therein a second end of the supporting member located outside the processing chamber, and is partitioned into a first space at a first end side and a second space at a second end side in a moving direction with respect to the second end. A pressure controller generates a pressure difference between the first space and the second space. The pressure difference allows the supporting member to be moved.