PURPOSE: To prevent the deformation of a flexible sheet and to evade shift of a transcribed image, by providing a pressure-contact member, a backup member, an attaching/detaching member for the backup member, etc. to the flexible sheet wound round a drum.

CONSTITUTION: A flexible sheet (dielectric sheet) 24 is wound round a hollow drum 11 of a drum device, and the edge of the sheet 24 is stuck to a coupled wall. A pressure-contact member such as a cleaning blade 32 is pressed to the sheet 24 in the axial direction of the drum 11. At the same time, a backup member such as a backup roller 33 touches the back side of the sheet 24. Thus the bending of the sheet 24 is avoided when the sheet is wound round the drum. As a result, the deformation is avoided for a thin flexible sheet wound round a drum, therefore, a shift of a transcribed image is prevented.