An image forming apparatus to remove a jammed printing medium and to prevent a transmission of fixing heat is provided. The image forming apparatus includes a fixing unit to fix a toner image into a printing medium when the toner image is transferred onto the printing medium, the fixing unit including a fixing frame on which a pair of fixing rollers are rotatably disposed, at least one discharge roller disposed on the fixing frame, and a discharge guide movable with respect to the fixing frame, and having a plurality of guide protrusions to guide the printing medium toward the discharge roller when the printing medium passes through the fixing unit. The fixing unit additionally includes a cover to cover the discharge roller and the discharge guide, and a plurality of heat dissipating ribs extending from an outer surface of the cover. The heat dissipating ribs have a height and are arranged at a gap from each other so as to prevent a user's hand from directly contacting the cover.