To provide an image forming apparatus constituted so as to prevent curl up of a cleaning member such as a cleaning blade for cleaning an intermediate transfer belt.

In a printer which forms a color image by sequentially performing primary transfer of toner images of each color formed on a photosensitive drum on the intermediate transfer belt 6 without mis-registration and performing secondary transfer of the image of each color transferred on the intermediate transfer belt 6 on paper in block, it is constituted so that relation of WD>WBC>WS is satisfied when length of a toner pattern 70 for preventing the curl up of a blade which is formed on the intermediate transfer belt 6 in the main scanning direction is defined as WD, length (belt cleaning width) of the belt cleaning blade 81 for cleaning on the intermediate transfer belt 6 in the main scanning direction is defined as WBC and the maximum length of the paper to be used in the main scanning direction is defined as WS.