To provide a sealing system between partition wall and a ceiling in a manufacturing factory, ensuring sealing between the partition wall for forming a clean room to be arranged along the inside of a building wall and the ceiling arranged on a large roof in an elevatable structure so as to move up and down together with the large roof while following the ceiling elevated together with the large roof.

The partition wall 1 for forming the clean room to be arranged along the inside of the building wall is arranged to self-stand on a floor surface. A flexible sheet 3 is arranged between the upper end of the partition wall 1 and the ceiling 2 arranged to follow the elevation of the large roof at the lower position of the large roof, and then connected thereto in a sealed manner.