An image forming apparatus includes an image bearing member, a conductive member, a bias application device, and a control portion. The image bearing member has a photosensitive layer formed on an outer peripheral surface thereof. The conductive member is disposed so as to make contact with an inner peripheral surface of the image bearing member and has a dielectric property. The bias application device applies a bias including an alternating current bias to the conductive member. The control portion controls the bias application device. The image forming apparatus is capable of executing a heating-up mode in which an alternating current bias having a peak-to-peak value twice or more as large as a discharge start voltage between the conductive member and the image bearing member is applied to the conductive member to cause the surface of the image bearing member to be heated up.