An image forming device includes an image carrier on the surface of which a toner image is formed, a cleaning member arranged in contact with, for cleaning, the surface of the image carrier, a charging member for electrostatically charging the image carrier, a bias applying device, and a control portion. The bias applying device applies a charging bias having DC and AC biases superimposed on each other to the charging member. The control portion controls the charging bias applied to the charging member by the bias applying device. As the AC bias applied to the charging member, the control portion uses, in a first period from the start of use of the image carrier to a predetermined time thereafter, a first AC bias and, in a second period subsequent to the first period, a second AC bias higher than the first AC bias.