An image forming apparatus is provided. The image forming apparatus includes a fixing unit to thermally fix an image transferred onto a sheet, a discharge unit to discharge the sheet carried from the fixing unit outside the image forming apparatus through a discharge path, a swingable member to be swung by the sheet being discharged, a swing-detectable sensor to detect swing movement of the swingable member being swung by the sheet, and a judging unit to judge as to whether the sheet is in one-sided alignment, in which the sheet is aligned to one of the widthwise sides in the discharge path based on result detected by the swing-detectable sensor.