An image forming apparatus includes an image carrier, a developer carrier, a toner carrier, a bias voltage control unit, and a detection unit. The developer carrier carries a developer layer containing toner, an additive and carriers thereon. The toner carrier supplies toner to the image carrier. The bias voltage control unit changes bias voltage setting from ordinary developing mode to toner removing mode when the detection unit detects toner adhesion in excess of a threshold value on the toner carrier. In the toner removing mode, the bias voltage control unit sets the bias voltage to be applied to the image carrier, the developer carrier, and the toner carrier so that only the additive remains on the circumferential surface of the toner carrier, and the developer layer carried on the developer carrier contacts the circumferential surface of the toner carrier with a larger force, as compared with the ordinary developing mode.