An image forming apparatus includes an image bearing member, a charging device to apply a charging bias, a developing device to develop a latent electrostatic image with toner, a transfer device to transfer the toner image to a recording medium, a fixing device to fix the toner image on the recording medium, an image formation speed switching device to switch from one image formation speed to another speed, a storage device to store a charging current target of the charging bias for each image formation speed, an electric current detection device to detect electric current flown through the charging device, and an AC voltage adjustment device to adjust AC voltage of the charging bias applied to the charging device. The charging current target is set for each of at least two image formation speeds such that each AC voltage adjusted by the AC voltage adjustment device is substantially the same.