Charging device, process cartridge, image forming apparatus, and assembly

To provide a charging device that prevents the occurrence of a stripe-like image defect.SOLUTION: A charging device comprises: a charging roll; and a cleaning roll that has a core grid and a foam elastic layer provided on an outer peripheral surface of the core grid, and rotates in contact with a surface of the charging roll, the cleaning roll having tips of cell skeletons projecting on the surface of the foam elastic layer in a number of 25/mm2 or more and 50/mm2 or less, and being arranged in contact with the charging roll in a state where the compressibility ratio of the foam elastic layer represented by the following formula (1) becomes 30% or less. Formula (1): compressibility ratio (%)=(r1/2+r2/2-d)/t1×100. In the formula (1), r1 is the outer diameter (mm) of the cleaning roll, r2 is the outer diameter (mm) of the charging roll, d is the inter-axis distance (mm) between the charging roll and the cleaning roll, and t1 is the thickness (mm) of the foam elastic layer of the cleaning roll.SELECTED DRAWING: Figure 1