An image forming apparatus has a photosensitive member, a charging member, an exposing device, a developing device, a transfer member, a polishing member, a driving device, a voltage applying device, a torque detector, and a control portion. The photosensitive member has a photosensitive layer and a surface protection layer formed on the surface of the photosensitive layer. The polishing member has an elastic layer on its circumferential surface, and rotates with a linear velocity difference from that of the photosensitive member. The torque detector detects the torque of the driving device. The control portion estimates an attachment condition of discharge products to the surface of the photosensitive member based on the torque of the driving device detected by the torque detector. When the torque is equal to or higher than a predetermined value, the control portion performs an image degradation suppression process.