An image forming apparatus sequentially transfers toner images formed on a plurality of photosensitive drums onto an intermediate transfer member or a transfer material to form an image. The image forming apparatus includes an intermediate transfer belt provided with electrical conductivity, and a power supply for applying a voltage to a secondary transfer roller to pass a current from the secondary transfer roller to the plurality of photosensitive drums via the intermediate transfer belt, thus primarily transferring the toner images from the plurality of photosensitive drums onto the intermediate transfer belt.