An image forming apparatus includes an image carrying member, an intermediate transfer belt, a primary transfer roller, a first belt support roller, a secondary transfer roller, a second belt support roller, a current feeder, a controller, a current sensor, and a rectifier. The current sensor has a lead member. The rectifier shuts off a current passing from the second belt support roller to the ground if the voltage on the second belt support roller is less than a predetermined reference voltage. The controller controls the output current such that the secondary transfer current has a current value resulting from subtracting a leak current from the output current and, when the lead member is in a conducting state, keeps the voltage on the second belt support roller less than the reference voltage.