An image forming apparatus includes a photoconductor, a charging roller configured to charge the photoconductor, and a self-excited oscillation circuit. The image forming apparatus includes a transformer including a primary coil and a secondary coil, the transformer being configured to produce, at the secondary coil, a voltage applied to the charging roller, in accordance with the primary coil being driven by the self-excited oscillation circuit. The image forming apparatus includes a controller configured to control, at start-up of the self-excited oscillation circuit, the self-excited oscillation circuit to allow an amount of a current flowing through the primary coil to be larger than an amount of a current flowing from the photoconductor through the secondary coil, via the charging roller.