An image forming apparatus is provided with an image bearing member, charging means which has a discharge wire and a grid and which charges the image bearing member, first current supply control means which controls a current supply to the discharge wire, second current supply control means which controls a current supply to the grid, potential setting means which sets a potential value on the image bearing means to be charged by the charging means, first current supply condition selecting means which selects a current control condition of the first current supply control means or the second current supply control means according to the set potential, and second current supply condition selecting means which selects a current control condition for the other current supply control means based on the determined current control condition. Thus a potential regulation over a wide range can be achieved within a short time, without involving an increase of the current to the discharge wire.