A cleaning brush can prevent "image deletion" and "toner filming" attributable to uneven wear, a streak, an injury, etc. on an image bearing member caused by endurance, and a streak on the image bearing member or the like surface-roughened for the purposes of a long life and a high quality of image. In an image forming apparatus provided with the cleaning brush for removing any untransferred toner residual on the image bearing member, that portion of the cleaning brush which is in contact with the image bearing member is constituted by at least two kinds of hairs having different thicknesses, and the deformation resistivity .rho. of that portion of each hair which is in contact with the image bearing member is set to 1.15 N or greater.