PURPOSE: To prevent the distortion of an image by moving a photosensitive body in the axial direction in processes other than the image forming process.

CONSTITUTION: When the image is formed, a clutch 16 is connected and a photosensitive body 1 is not moved in the axial direction and is rotated there. In processes other than the image forming process, for example, the preparatory rotation process of the photosensitive body, the post-rotation process for cleaning, or the like, the clutch 16 is disconnected to stop gears 14 and 15 and a roll 20 and a cam groove S is turned through gears 3 and 13 to move the photosensitive body 1 in the axial direction. In this case, the time when the clutch 16 is disconnected to stop gears 15 and 14 is properly set by a controller 17 so that the photosensitive body 1 is repeatedly stopped in the same position in the axial direction. Thus, the distortion of the image does not occur.