An image forming apparatus including a motor for rotating a stirring member and a cleaner to which a driving force of the motor is transmitted via a transmission mechanism. In a buffer container of a toner replenishment device of a developing device, a gear connected to a restriction member for stirring toner in the buffer container and restricting toner from dropping into a toner conveying section and a cleaning member for cleaning the detection surface of a toner sensor are driven by a motor. A CPU controls a timing at which a clutch stops transmission of the driving force from the motor to the gear, based on a result of detection by a flag sensor that detects an amount of rotation of the gear, and a rotational speed of the motor.

A cleaning device includes a state determination processing portion and an abnormality determination processing portion. The state determination processing portion, when a movement detecting portion does not detect a moving body before a predetermined specific time passes since a start of a drive of a drive source, determines a drive state of the drive source based on a detection result of a current detecting portion. The abnormality determination processing portion determines that an abnormality has occurred in the movement detecting portion when the state determination processing portion determines that the drive source is being driven, and determines that an abnormality has occurred in the drive source when the state determination processing portion determines that the drive source is not being driven.

An image forming apparatus includes an apparatus body, an image bearing member, and a process unit attached to the apparatus body. The process unit includes a frame including a storage portion configured to store developer, a developer bearing member configured to supply developer to the image bearing member to develop an electrostatic latent image, and a circuit board attached to the frame. The circuit board includes a light emitting portion configured to emit light, and a light receiving portion configured to receive the light emitted from the light emitting portion and having passed through an interior of the storage portion.