An image forming apparatus includes a rotatable image bearing member, a developing device including a developing carrying member and configured to develop an electrostatic image formed on the image bearing member with developer, an electrostatic capacity detecting portion configured to detect information on electrostatic capacity between the developer carrying member and the image bearing member, and a toner content detecting portion configured to detect information on a toner content of the developer accommodated in a developing container. On the basis of the detected electrostatic capacity and the detected toner content, a controller controls a driving speed at which the developer carrying member is rotationally driven.