An image forming apparatus includes a first power source configured to supply charging voltage to a first charging unit, and a second power source configured to supply predetermined voltage to at least one of a second charging unit, a second developing member, and a second transfer unit. The first and the second power sources are grounded via a common resistor component. When the second power source in a state of supplying no voltage or supplying voltage lower than the predetermined voltage at a first timing starts supplying the predetermined voltage while the first power source is supplying the charging voltage, a control unit causes a separating mechanism to move a first developing member to a separation position before a second timing at which an area of a first photosensitive member that is at a charging position at the first timing reaches a developing position.