An image forming apparatus having; image supporting members provided for a plurality of colors; chargers to be impressed with charging biases to charge the respective image supporting members; developing devices to be impressed with developing biases to develop latent images formed on the image supporting members; a charging bias power supply, including high-voltage DC power supply circuits and an AC power supply circuit, for applying the charging biases, which are generated by superposition of direct-current voltages and an alternate-current voltage, to the chargers; and a control circuit that performs stop processing to stop applications of the charging biases and the developing biases. The control circuit performs processing to attenuate each of the direct-current voltages and each of the developing biases, and after all the direct-current voltages have become a predetermined stop potential, the control circuit performs processing to stop the outputs of the direct-current voltages and the alternate-current voltage.