An image forming apparatus has a transfer belt and a plural number of image forming units. The transfer belt has a sucking/feeding surface for sucking and feeding a sheet of transfer medium, and the sucking/feeding surface faces downward slanting from a vertical direction. The plural number of image forming units face the sucking/feeding surface of the transfer belt, and are arranged side by side along the transfer belt rotating direction. The transfer members are located inside a loop of the transfer belt and are pressed against a surface of the transfer belt on the reverse of the sucking/feeding surface in positions opposite photosensitive drums via the transfer belt. The transfer members apply a charge of a polarity opposite to that of toner to the transfer medium via the transfer belt. The transfer members are made of a conductive material.