An image forming apparatus includes an image carrier to carry a toner image. A transfer unit transfers the toner image to a sheet. A fixing unit fixes the toner image on the sheet. The sheet with the image is discharged to a sheet discharge tray. A circular conveyance path turns over the sheet past the transfer unit and the fixing unit and passes the sheet through the transfer unit and the fixing unit again. A heat amount setting section sets an amount of heat applied by the fixing unit when fixing of the sheet is executed. In duplex printing, a first heat amount for fixing the toner image on a first side of the sheet is smaller than a reference heat amount for simplex printing whereas a second heat amount for fixing the toner image on a second side of the sheet is larger than the reference heat amount.