A charge apparatus charges by uniformly superimposing an alternate current bias voltage with a fixed frequency over a direct current bias voltage as the charge bias voltage on a photosensitive member. An exposure apparatus exposes the surface of the charged photosensitive member based on image data, and writes a latent image, and a developing apparatus supplies toner to and makes visible the latent image formed on the surface of the photosensitive member. A transfer apparatus transfers the visible image on the photosensitive member to a transfer medium, and a cleaning apparatus cleans the surface of the photosensitive member after transfer.