An image-forming apparatus for forming an image, especially a halftone image, by using a photosensitive member, having a charging member for charging the photosensitive member, a mechanism for relatively moving the charging member and the photosensitive member, a voltage source for applying an oscillatory voltage to the charging member such that a Vp/f ratio is about from 0.08 to 0.42, wherein the Vp represents a relative moving speed between the charging member and the photosensitive member and the f represents a frequency of the oscillatory voltage, an exposing member for exposing the charged photosensitive member to form an electrostatic latent image, and a developing unit for developing the electrostatic latent image.