An example image forming apparatus includes a main body, a printing engine to be disposed in the main body to form an image on a printing medium, a fixing apparatus including a fixing roller and a fixing belt disposed to face the fixing roller, and a jam prevention apparatus including a fixed frame disposed adjacent to the fixing apparatus, and a movable apparatus to be detachably fastened to the fixed frame through a plurality of adjusting screws, to adjust a gap with the fixing belt according to a fastening direction of the plurality of adjusting screws.