An image forming apparatus includes a plurality of image carriers arranged side by side along the outer surface of a conveying portion of a transfer belt. The transfer belt is stretched between a first upstream roller and a second downstream roller. An image forming medium is conveyed on the belt so as to have multiple color images transferred thereto. The transfer belt has a swing lever so as to move the belt between a horizontal full color position and an inclined monochrome position. A stationary support roller which is arranged within the transfer belt and at a position nearer to the second downstream roller maintains a position of the image forming medium constant even when a monochrome image is being transferred. In addition, an electrostatic attraction roller located outside the transfer belt is arranged at a specific angle relative to the first roller to assist in the attraction of the image forming medium to the transfer belt.